04-28-2023, 06:04 AM
Python Async With Statement — Simplifying Asynchronous Code
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<div class="kksr-legend" style="font-size: 19.2px;"> 5/5 – (1 vote) </div>
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<p>To speed up my code, I just decided to (finally) dive into Python’s <code>async with</code> statement. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> In this article, you’ll find some of my learnings – let’s go! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">What Is Python Async With?</h2>
<p class="has-global-color-8-background-color has-background">Python’s <code>async with</code> statement is a way to work with <strong>asynchronous context managers</strong>, which can be really useful when dealing with I/O-bound tasks, such as reading or writing files, making <a rel="noreferrer noopener" href="https://blog.finxter.com/python-requests-library/" data-type="post" data-id="37796" target="_blank">HTTP requests</a>, or interacting with databases. These tasks normally block your program’s execution, involving waiting for external resources. But using <code>async with</code>, you can perform multiple tasks concurrently! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f389.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>Let’s see some code. Picture this scenario: you’re using <a rel="noreferrer noopener" href="https://docs.python.org/3/library/asyncio-task.html" target="_blank"><code>asyncio</code></a> and <a href="https://stackoverflow.com/questions/37465816/async-with-in-python-3-4"><code>aiohttp</code></a> to fetch some content over HTTP. If you were to use a regular <code>with</code> statement, your code would look like this:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
import aiohttp
import asyncio async def fetch(url): with aiohttp.ClientSession() as session: response = await session.get(url) content = await response.read() print(asyncio.run(fetch("https://example.com")))
</pre>
<p>But see the problem? <strong>This would block the event loop</strong>, making your app slower <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f612.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />. </p>
<p>The solution is using <code>async with</code> alongside a context manager that supports it:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
import aiohttp
import asyncio async def fetch(url): async with aiohttp.ClientSession() as session: response = await session.get(url) content = await response.read() print(asyncio.run(fetch("https://example.com")))
</pre>
<p>Thanks to <code>async with</code>, your code won’t block the event loop while working with context managers, making your program more efficient and responsive! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f31f.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>No worries if you didn’t quite get it yet. Keep reading! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Python Async With Examples</h2>
<div class="wp-block-image">
<figure class="aligncenter size-full"><img loading="lazy" decoding="async" width="743" height="575" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-233.png" alt="" class="wp-image-1313583" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-233.png 743w, https://blog.finxter.com/wp-content/uplo...00x232.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
</div>
<p>The <code>async with</code> statement is used when you want to run a certain operation concurrently and need to manage resources effectively, such as when dealing with <strong>I/O-bound tasks like fetching a web page</strong> <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f310.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />. </p>
<p>Let’s jump into an example using an <code>asyncio</code>-based library called <code><a href="https://blog.finxter.com/how-to-install-aiohttp-in-python/" data-type="post" data-id="35818" target="_blank" rel="noreferrer noopener">aiohttp</a></code>.</p>
<p>Here’s how you can make an <a href="https://blog.finxter.com/python-one-line-http-get/" data-type="post" data-id="12832" target="_blank" rel="noreferrer noopener">HTTP GET</a> request using an <code>async with</code> statement and aiohttp’s <code>ClientSession</code> class:</p>
<div class="wp-block-image">
<figure class="aligncenter size-large"><img decoding="async" loading="lazy" width="1024" height="527" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-297-1024x527.png" alt="" class="wp-image-1323227" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-297-1024x527.png 1024w, https://blog.finxter.com/wp-content/uplo...00x155.png 300w, https://blog.finxter.com/wp-content/uplo...68x396.png 768w, https://blog.finxter.com/wp-content/uplo...ge-297.png 1163w" sizes="(max-width: 1024px) 100vw, 1024px" /></figure>
</div>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import aiohttp
import asyncio async def fetch_page(session, url): async with session.get(url) as response: return await response.text() async def main(): async with aiohttp.ClientSession() as session: content = await fetch_page(session, 'https://example.com') print(content) loop = asyncio.get_event_loop()
loop.run_until_complete(main())
</pre>
<p>In the example above<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f446.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />, you use an <code>async with</code> statement in the <code>fetch_page</code> function to ensure that the response is properly acquired and released. You can see a similar pattern in the <code>main</code> function, where the <code>aiohttp.ClientSession</code> is managed using an <code>async with</code> statement. This ensures that resources such as network connections are handled properly<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/2705.png" alt="✅" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</p>
<p>Now, let’s discuss some key entities in this example:</p>
<ul>
<li><strong><code>session</code></strong>: An instance of the <code>aiohttp.ClientSession</code> class, used to manage HTTP requests<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4e8.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>url</code></strong>: A variable representing the URL of the web page you want to fetch<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f310.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>response</code></strong>: The HTTP response object returned by the server<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f516.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>clientsession</code></strong>: A class provided by the <code>aiohttp</code> library to manage HTTP requests and responses<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f309.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>text()</code></strong>: A method provided by the <code>aiohttp</code> library to read the response body as text<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4c3.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>async with</code> statement</strong>: A special construct to manage resources within an asynchronous context<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f504.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
</ul>
<h2 class="wp-block-heading">Async With Await</h2>
<div class="wp-block-image">
<figure class="aligncenter size-full"><img decoding="async" loading="lazy" width="743" height="495" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-229.png" alt="" class="wp-image-1313579" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-229.png 743w, https://blog.finxter.com/wp-content/uplo...00x200.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
</div>
<p>In Python, the <code>await</code> keyword is used with asynchronous functions, which are defined using the <code>async def</code> syntax. Asynchronous functions, or coroutines, enable non-blocking execution and allow you to run multiple tasks concurrently without the need for threading or multiprocessing.</p>
<p class="has-global-color-8-background-color has-background">In the context of the <code>async with</code> statement, <code>await</code> is used to wait for the asynchronous context manager to complete its tasks. The <code>async with</code> statement is used in conjunction with an asynchronous context manager, which is an object that defines <code><a href="https://blog.finxter.com/python-__aenter__-magic-method/" data-type="post" data-id="142714" target="_blank" rel="noreferrer noopener">__aenter__()</a></code> and <code><a href="https://blog.finxter.com/python-__aexit__-magic-method/" data-type="post" data-id="142829" target="_blank" rel="noreferrer noopener">__aexit__()</a></code> asynchronous methods. These methods are used to set up and tear down a context for a block of code that will be executed asynchronously.</p>
<p>Here’s an example of how <code>async with</code> and <code>await</code> are used together:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="7,11" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import aiohttp
import asyncio async def fetch(url): async with aiohttp.ClientSession() as session: async with session.get(url) as response: return await response.text() async def main(): url = 'https://example.com/' html = await fetch(url) print(html) loop = asyncio.get_event_loop()
loop.run_until_complete(main())
</pre>
<p>In this example, the <code>fetch</code> function is an asynchronous function that retrieves the content of a given URL using the <code>aiohttp</code> library. </p>
<p>The <code>async with</code> statement is used to create an asynchronous context manager for the <code>aiohttp.ClientSession()</code> and <code>session.get(url)</code> objects. </p>
<p>The <code>await</code> keyword is then used to wait for the response from the <code>session.get()</code> call to be available, and to retrieve the text content of the response.</p>
<h2 class="wp-block-heading">Async With Open</h2>
<div class="wp-block-image">
<figure class="aligncenter size-full"><img decoding="async" loading="lazy" width="743" height="495" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-230.png" alt="" class="wp-image-1313580" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-230.png 743w, https://blog.finxter.com/wp-content/uplo...00x200.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
</div>
<p>By using “<code>async with open</code>“, you can open files in your asynchronous code without blocking the execution of other coroutines.</p>
<p>When working with async code, it’s crucial to avoid blocking operations. To tackle this, some libraries provide asynchronous equivalents of “<code>open</code>“, allowing you to seamlessly read and write files in your asynchronous code. </p>
<p>For example:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="4" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import aiofiles async def read_file(file_path): async with aiofiles.open(file_path, 'r') as file: contents = await file.read() return contents
</pre>
<p>Here, we use the <code><a href="https://github.com/Tinche/aiofiles" target="_blank" rel="noreferrer noopener">aiofiles</a></code> library, which provides an asynchronous file I/O implementation. With “<code>async with</code>“, you can <a href="https://blog.finxter.com/python-open-function/" data-type="post" data-id="24793" target="_blank" rel="noreferrer noopener">open the file</a>, perform the desired operations (like reading or writing), and the file will automatically close when it’s no longer needed – all without blocking your other async tasks. Neat, huh? <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f913.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>Remember, it’s essential to use an asynchronous file I/O library, like <code>aiofiles</code>, when working with <code>async with open</code>. This ensures that your file operations won’t block the rest of your coroutines and keep your async code running smoothly. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4aa-1f3fc.png" alt="??" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Async With Yield</h2>
<p>When working with Python’s async functions, you might wonder how to use the <code>yield</code> keyword within an <code>async with</code> statement. In this section, you’ll learn how to effectively combine these concepts for efficient and readable code.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f60a.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p class="has-base-2-background-color has-background"><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4a1.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> <strong>Recommended</strong>: <a href="https://blog.finxter.com/yield-keyword-in-python-a-simple-illustrated-guide/" data-type="post" data-id="14682" target="_blank" rel="noreferrer noopener">Understanding Python’s <code>yield</code> Keyword</a></p>
<p>First, it’s essential to understand that you cannot use the standard <code>yield</code> with async functions. Instead, you need to work with asynchronous generators, introduced in <a href="https://blog.finxter.com/how-to-check-your-python-version/" data-type="post" data-id="1371" target="_blank" rel="noreferrer noopener">Python 3.6</a> and PEP 525. Asynchronous generators allow you to yield values concurrently using the <code>async def</code> keyword and help you avoid blocking operations.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>To create an asynchronous <a href="https://blog.finxter.com/python-generator-expressions/" data-type="post" data-id="975287" target="_blank" rel="noreferrer noopener">generator</a>, you can define a function with the <code>async def</code> keyword and use the <code>yield</code> statement inside it, like this:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import asyncio async def asyncgen(): yield 1 yield 2
</pre>
<p>To consume the generator, use <code>async for</code> like this:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">async def main(): async for i in asyncgen(): print(i) asyncio.run(main())
</pre>
<p>This code will create a generator that yields values asynchronously and print them using an async context manager. This approach allows you to <a href="https://codereview.stackexchange.com/questions/241829/wrapping-an-asynchronous-generator-in-python" target="_blank" rel="noreferrer noopener">wrapp an asynchronous generator</a> in a friendly and readable manner.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f389.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>Now you know how to use the <code>yield</code> keyword within an <code>async with</code> statement in Python. It’s time to leverage the power of asynchronous generators in your code!<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Async With Return</h2>
<div class="wp-block-image">
<figure class="aligncenter size-full"><img decoding="async" loading="lazy" width="743" height="499" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-231.png" alt="" class="wp-image-1313581" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-231.png 743w, https://blog.finxter.com/wp-content/uplo...00x201.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
</div>
<p>The <code>async with</code> statement is used to simplify your interactions with asynchronous context managers in your code, and yes, it can return a value as well! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f603.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>When working with <code>async with</code>, the value returned by the <code><a rel="noreferrer noopener" href="https://blog.finxter.com/python-__enter__-magic-method/" data-type="post" data-id="140907" target="_blank">__enter__()</a></code> method of an asynchronous context manager gets bound to a target variable. This helps you manage resources effectively in your async code. </p>
<p>For instance:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">async def fetch_data(url): async with aiohttp.ClientSession() as session: async with session.get(url) as response: data = await response.json() return data
</pre>
<p>In this example, the <code>response</code> object is the value returned by the context manager’s <code>.__enter__()</code> method. Once the <code>async with</code> block is executed, the <code><a href="https://blog.finxter.com/how-to-return-a-json-object-from-a-function-in-python/" data-type="post" data-id="985215" target="_blank" rel="noreferrer noopener">response.json()</a></code> method is awaited to deserialize the JSON data, which is then returned to the caller <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f44c.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</p>
<p>Here are a few key takeaway points about returning values with <code>async with</code>:</p>
<ul>
<li><code>async with</code> simplifies handling of resources in asynchronous code.</li>
<li>The value returned by the <code>.__enter__()</code> method is automatically bound to a target variable within the <code>async with</code> block.</li>
<li>Returning values from your asynchronous context managers easily integrates with your async code.</li>
</ul>
<h2 class="wp-block-heading">Advanced Usage of Async With</h2>
<figure class="wp-block-image size-full"><img decoding="async" loading="lazy" width="743" height="531" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-232.png" alt="" class="wp-image-1313582" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-232.png 743w, https://blog.finxter.com/wp-content/uplo...00x214.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
<p>As you become more familiar with Python’s <code>async with</code> statement, you’ll discover advanced techniques that can greatly enhance your code’s efficiency and readability. This section will cover four techniques: </p>
<ul>
<li>Async With Timeout, </li>
<li>Async With Multiple, </li>
<li>Async With Lock, and </li>
<li>Async With Context Manager</li>
</ul>
<h3 class="wp-block-heading">Async With Timeout</h3>
<p>When working with concurrency, it’s essential to manage timeouts effectively. In <code>async with</code> statements, you can ensure a block of code doesn’t run forever by implementing an async timeout. This can help you handle scenarios where network requests or other I/O operations take too long to complete.</p>
<p><a href="https://stackoverflow.com/questions/37465816/async-with-in-python-3-4">Here’s an example</a> of how you can define an async with statement with a timeout:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
import asyncio
import aiohttp async def fetch_page(session, url): async with aiohttp.Timeout(10): async with session.get(url) as response: assert response.status == 200 return await response.read()
</pre>
<p>This code sets a 10-second timeout to fetch a web page using the <code>aiohttp</code> library.</p>
<h3 class="wp-block-heading">Async With Multiple</h3>
<p>You can use multiple <code>async with</code> statements simultaneously to work with different resources, like file access or database connections. Combining multiple <code>async with</code> statements enables better resource management and cleaner code:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
async def two_resources(resource_a, resource_b): async with aquire_resource_a(resource_a) as a, aquire_resource_b(resource_b) as b: await do_something(a, b)
</pre>
<p>This example acquires both resources asynchronously and then performs an operation using them.</p>
<h3 class="wp-block-heading">Async With Lock</h3>
<p>Concurrency can cause issues when multiple tasks access shared resources. To protect these resources and prevent race conditions, you can use <code>async with</code> along with Python’s <code>asyncio.Lock()</code> class:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
import asyncio lock = asyncio.Lock() async def my_function(): async with lock: # Section of code that must be executed atomically.
</pre>
<p>This code snippet ensures that the section within the <code>async with</code> block is executed atomically, protecting shared resources from being accessed concurrently.</p>
<h3 class="wp-block-heading">Async With Context Manager</h3>
<p>Creating your own context managers can make it easier to manage resources in asynchronous code. By defining an <code>async def __aenter__()</code> and an <code>async def __aexit__()</code> method in your class, you can use it within an <code>async with</code> statement:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
class AsyncContextManager: async def __aenter__(self): # Code to initialize resource return resource async def __aexit__(self, exc_type, exc, tb): # Code to release resource async def demo(): async with AsyncContextManager() as my_resource: # Code using my_resource
</pre>
<p>This custom context manager initializes and releases a resource within the <code>async with</code> block, simplifying your asynchronous code and making it more Pythonic.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/2728.png" alt="✨" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Error Handling and Exceptions</h2>
<figure class="wp-block-image size-full"><img decoding="async" loading="lazy" width="743" height="546" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-234.png" alt="" class="wp-image-1313584" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-234.png 743w, https://blog.finxter.com/wp-content/uplo...00x220.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
<p>When working with <strong>Python’s Async With Statement</strong>, handling errors and exceptions properly is essential to ensure your asynchronous code runs smoothly. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> Using <a href="https://blog.finxter.com/python-try-except-an-illustrated-guide/" data-type="post" data-id="367118" target="_blank" rel="noreferrer noopener">try-except blocks</a> and well-structured clauses can help you manage errors effectively.</p>
<p>Be aware of syntax errors, which may occur when using async with statements. To avoid SyntaxError, make sure your Python code is properly formatted and follows PEP 343’s guidelines. If you come across an error while performing an IO operation or dealing with external resources, it’s a good idea to handle it with an <code>except</code> clause. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f60e.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>In the case of exceptions, you might want to apply cleanup code to handle any necessary actions before your program closes or moves on to the next task. One way to do this is by wrapping your <code>async with</code> statement in a try-except block, and then including a <code>finally</code> clause for the cleanup code. </p>
<p>Here’s an example:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
try: async with some_resource() as resource: # Perform your IO operation or other tasks here
except YourException as e: # Handle the specific exception here
finally: # Add cleanup code here
</pre>
<p>Remember, you need to handle exceptions explicitly in the parent coroutine if you want to prevent them from canceling the entire task. In the case of multiple exceptions or errors, using <code>asyncio.gather</code> can help manage them effectively. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4aa.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p class="has-base-2-background-color has-background"><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4a1.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> <strong>Recommended</strong>: <a href="https://blog.finxter.com/python-cheat-sheet/" data-type="post" data-id="305" target="_blank" rel="noreferrer noopener">Python Beginner Cheat Sheet: 19 Keywords Every Coder Must Know</a></p>
</div>
https://www.sickgaming.net/blog/2023/04/...nous-code/
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<p>To speed up my code, I just decided to (finally) dive into Python’s <code>async with</code> statement. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> In this article, you’ll find some of my learnings – let’s go! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">What Is Python Async With?</h2>
<p class="has-global-color-8-background-color has-background">Python’s <code>async with</code> statement is a way to work with <strong>asynchronous context managers</strong>, which can be really useful when dealing with I/O-bound tasks, such as reading or writing files, making <a rel="noreferrer noopener" href="https://blog.finxter.com/python-requests-library/" data-type="post" data-id="37796" target="_blank">HTTP requests</a>, or interacting with databases. These tasks normally block your program’s execution, involving waiting for external resources. But using <code>async with</code>, you can perform multiple tasks concurrently! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f389.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>Let’s see some code. Picture this scenario: you’re using <a rel="noreferrer noopener" href="https://docs.python.org/3/library/asyncio-task.html" target="_blank"><code>asyncio</code></a> and <a href="https://stackoverflow.com/questions/37465816/async-with-in-python-3-4"><code>aiohttp</code></a> to fetch some content over HTTP. If you were to use a regular <code>with</code> statement, your code would look like this:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
import aiohttp
import asyncio async def fetch(url): with aiohttp.ClientSession() as session: response = await session.get(url) content = await response.read() print(asyncio.run(fetch("https://example.com")))
</pre>
<p>But see the problem? <strong>This would block the event loop</strong>, making your app slower <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f612.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />. </p>
<p>The solution is using <code>async with</code> alongside a context manager that supports it:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
import aiohttp
import asyncio async def fetch(url): async with aiohttp.ClientSession() as session: response = await session.get(url) content = await response.read() print(asyncio.run(fetch("https://example.com")))
</pre>
<p>Thanks to <code>async with</code>, your code won’t block the event loop while working with context managers, making your program more efficient and responsive! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f31f.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>No worries if you didn’t quite get it yet. Keep reading! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f447.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Python Async With Examples</h2>
<div class="wp-block-image">
<figure class="aligncenter size-full"><img loading="lazy" decoding="async" width="743" height="575" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-233.png" alt="" class="wp-image-1313583" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-233.png 743w, https://blog.finxter.com/wp-content/uplo...00x232.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
</div>
<p>The <code>async with</code> statement is used when you want to run a certain operation concurrently and need to manage resources effectively, such as when dealing with <strong>I/O-bound tasks like fetching a web page</strong> <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f310.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />. </p>
<p>Let’s jump into an example using an <code>asyncio</code>-based library called <code><a href="https://blog.finxter.com/how-to-install-aiohttp-in-python/" data-type="post" data-id="35818" target="_blank" rel="noreferrer noopener">aiohttp</a></code>.</p>
<p>Here’s how you can make an <a href="https://blog.finxter.com/python-one-line-http-get/" data-type="post" data-id="12832" target="_blank" rel="noreferrer noopener">HTTP GET</a> request using an <code>async with</code> statement and aiohttp’s <code>ClientSession</code> class:</p>
<div class="wp-block-image">
<figure class="aligncenter size-large"><img decoding="async" loading="lazy" width="1024" height="527" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-297-1024x527.png" alt="" class="wp-image-1323227" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-297-1024x527.png 1024w, https://blog.finxter.com/wp-content/uplo...00x155.png 300w, https://blog.finxter.com/wp-content/uplo...68x396.png 768w, https://blog.finxter.com/wp-content/uplo...ge-297.png 1163w" sizes="(max-width: 1024px) 100vw, 1024px" /></figure>
</div>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import aiohttp
import asyncio async def fetch_page(session, url): async with session.get(url) as response: return await response.text() async def main(): async with aiohttp.ClientSession() as session: content = await fetch_page(session, 'https://example.com') print(content) loop = asyncio.get_event_loop()
loop.run_until_complete(main())
</pre>
<p>In the example above<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f446.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />, you use an <code>async with</code> statement in the <code>fetch_page</code> function to ensure that the response is properly acquired and released. You can see a similar pattern in the <code>main</code> function, where the <code>aiohttp.ClientSession</code> is managed using an <code>async with</code> statement. This ensures that resources such as network connections are handled properly<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/2705.png" alt="✅" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</p>
<p>Now, let’s discuss some key entities in this example:</p>
<ul>
<li><strong><code>session</code></strong>: An instance of the <code>aiohttp.ClientSession</code> class, used to manage HTTP requests<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4e8.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>url</code></strong>: A variable representing the URL of the web page you want to fetch<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f310.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>response</code></strong>: The HTTP response object returned by the server<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f516.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>clientsession</code></strong>: A class provided by the <code>aiohttp</code> library to manage HTTP requests and responses<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f309.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>text()</code></strong>: A method provided by the <code>aiohttp</code> library to read the response body as text<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4c3.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
<li><strong><code>async with</code> statement</strong>: A special construct to manage resources within an asynchronous context<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f504.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</li>
</ul>
<h2 class="wp-block-heading">Async With Await</h2>
<div class="wp-block-image">
<figure class="aligncenter size-full"><img decoding="async" loading="lazy" width="743" height="495" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-229.png" alt="" class="wp-image-1313579" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-229.png 743w, https://blog.finxter.com/wp-content/uplo...00x200.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
</div>
<p>In Python, the <code>await</code> keyword is used with asynchronous functions, which are defined using the <code>async def</code> syntax. Asynchronous functions, or coroutines, enable non-blocking execution and allow you to run multiple tasks concurrently without the need for threading or multiprocessing.</p>
<p class="has-global-color-8-background-color has-background">In the context of the <code>async with</code> statement, <code>await</code> is used to wait for the asynchronous context manager to complete its tasks. The <code>async with</code> statement is used in conjunction with an asynchronous context manager, which is an object that defines <code><a href="https://blog.finxter.com/python-__aenter__-magic-method/" data-type="post" data-id="142714" target="_blank" rel="noreferrer noopener">__aenter__()</a></code> and <code><a href="https://blog.finxter.com/python-__aexit__-magic-method/" data-type="post" data-id="142829" target="_blank" rel="noreferrer noopener">__aexit__()</a></code> asynchronous methods. These methods are used to set up and tear down a context for a block of code that will be executed asynchronously.</p>
<p>Here’s an example of how <code>async with</code> and <code>await</code> are used together:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="7,11" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import aiohttp
import asyncio async def fetch(url): async with aiohttp.ClientSession() as session: async with session.get(url) as response: return await response.text() async def main(): url = 'https://example.com/' html = await fetch(url) print(html) loop = asyncio.get_event_loop()
loop.run_until_complete(main())
</pre>
<p>In this example, the <code>fetch</code> function is an asynchronous function that retrieves the content of a given URL using the <code>aiohttp</code> library. </p>
<p>The <code>async with</code> statement is used to create an asynchronous context manager for the <code>aiohttp.ClientSession()</code> and <code>session.get(url)</code> objects. </p>
<p>The <code>await</code> keyword is then used to wait for the response from the <code>session.get()</code> call to be available, and to retrieve the text content of the response.</p>
<h2 class="wp-block-heading">Async With Open</h2>
<div class="wp-block-image">
<figure class="aligncenter size-full"><img decoding="async" loading="lazy" width="743" height="495" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-230.png" alt="" class="wp-image-1313580" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-230.png 743w, https://blog.finxter.com/wp-content/uplo...00x200.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
</div>
<p>By using “<code>async with open</code>“, you can open files in your asynchronous code without blocking the execution of other coroutines.</p>
<p>When working with async code, it’s crucial to avoid blocking operations. To tackle this, some libraries provide asynchronous equivalents of “<code>open</code>“, allowing you to seamlessly read and write files in your asynchronous code. </p>
<p>For example:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="4" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import aiofiles async def read_file(file_path): async with aiofiles.open(file_path, 'r') as file: contents = await file.read() return contents
</pre>
<p>Here, we use the <code><a href="https://github.com/Tinche/aiofiles" target="_blank" rel="noreferrer noopener">aiofiles</a></code> library, which provides an asynchronous file I/O implementation. With “<code>async with</code>“, you can <a href="https://blog.finxter.com/python-open-function/" data-type="post" data-id="24793" target="_blank" rel="noreferrer noopener">open the file</a>, perform the desired operations (like reading or writing), and the file will automatically close when it’s no longer needed – all without blocking your other async tasks. Neat, huh? <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f913.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>Remember, it’s essential to use an asynchronous file I/O library, like <code>aiofiles</code>, when working with <code>async with open</code>. This ensures that your file operations won’t block the rest of your coroutines and keep your async code running smoothly. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4aa-1f3fc.png" alt="??" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Async With Yield</h2>
<p>When working with Python’s async functions, you might wonder how to use the <code>yield</code> keyword within an <code>async with</code> statement. In this section, you’ll learn how to effectively combine these concepts for efficient and readable code.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f60a.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p class="has-base-2-background-color has-background"><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4a1.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> <strong>Recommended</strong>: <a href="https://blog.finxter.com/yield-keyword-in-python-a-simple-illustrated-guide/" data-type="post" data-id="14682" target="_blank" rel="noreferrer noopener">Understanding Python’s <code>yield</code> Keyword</a></p>
<p>First, it’s essential to understand that you cannot use the standard <code>yield</code> with async functions. Instead, you need to work with asynchronous generators, introduced in <a href="https://blog.finxter.com/how-to-check-your-python-version/" data-type="post" data-id="1371" target="_blank" rel="noreferrer noopener">Python 3.6</a> and PEP 525. Asynchronous generators allow you to yield values concurrently using the <code>async def</code> keyword and help you avoid blocking operations.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>To create an asynchronous <a href="https://blog.finxter.com/python-generator-expressions/" data-type="post" data-id="975287" target="_blank" rel="noreferrer noopener">generator</a>, you can define a function with the <code>async def</code> keyword and use the <code>yield</code> statement inside it, like this:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">import asyncio async def asyncgen(): yield 1 yield 2
</pre>
<p>To consume the generator, use <code>async for</code> like this:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">async def main(): async for i in asyncgen(): print(i) asyncio.run(main())
</pre>
<p>This code will create a generator that yields values asynchronously and print them using an async context manager. This approach allows you to <a href="https://codereview.stackexchange.com/questions/241829/wrapping-an-asynchronous-generator-in-python" target="_blank" rel="noreferrer noopener">wrapp an asynchronous generator</a> in a friendly and readable manner.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f389.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>Now you know how to use the <code>yield</code> keyword within an <code>async with</code> statement in Python. It’s time to leverage the power of asynchronous generators in your code!<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Async With Return</h2>
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<figure class="aligncenter size-full"><img decoding="async" loading="lazy" width="743" height="499" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-231.png" alt="" class="wp-image-1313581" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-231.png 743w, https://blog.finxter.com/wp-content/uplo...00x201.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
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<p>The <code>async with</code> statement is used to simplify your interactions with asynchronous context managers in your code, and yes, it can return a value as well! <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f603.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>When working with <code>async with</code>, the value returned by the <code><a rel="noreferrer noopener" href="https://blog.finxter.com/python-__enter__-magic-method/" data-type="post" data-id="140907" target="_blank">__enter__()</a></code> method of an asynchronous context manager gets bound to a target variable. This helps you manage resources effectively in your async code. </p>
<p>For instance:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">async def fetch_data(url): async with aiohttp.ClientSession() as session: async with session.get(url) as response: data = await response.json() return data
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<p>In this example, the <code>response</code> object is the value returned by the context manager’s <code>.__enter__()</code> method. Once the <code>async with</code> block is executed, the <code><a href="https://blog.finxter.com/how-to-return-a-json-object-from-a-function-in-python/" data-type="post" data-id="985215" target="_blank" rel="noreferrer noopener">response.json()</a></code> method is awaited to deserialize the JSON data, which is then returned to the caller <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f44c.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" />.</p>
<p>Here are a few key takeaway points about returning values with <code>async with</code>:</p>
<ul>
<li><code>async with</code> simplifies handling of resources in asynchronous code.</li>
<li>The value returned by the <code>.__enter__()</code> method is automatically bound to a target variable within the <code>async with</code> block.</li>
<li>Returning values from your asynchronous context managers easily integrates with your async code.</li>
</ul>
<h2 class="wp-block-heading">Advanced Usage of Async With</h2>
<figure class="wp-block-image size-full"><img decoding="async" loading="lazy" width="743" height="531" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-232.png" alt="" class="wp-image-1313582" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-232.png 743w, https://blog.finxter.com/wp-content/uplo...00x214.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
<p>As you become more familiar with Python’s <code>async with</code> statement, you’ll discover advanced techniques that can greatly enhance your code’s efficiency and readability. This section will cover four techniques: </p>
<ul>
<li>Async With Timeout, </li>
<li>Async With Multiple, </li>
<li>Async With Lock, and </li>
<li>Async With Context Manager</li>
</ul>
<h3 class="wp-block-heading">Async With Timeout</h3>
<p>When working with concurrency, it’s essential to manage timeouts effectively. In <code>async with</code> statements, you can ensure a block of code doesn’t run forever by implementing an async timeout. This can help you handle scenarios where network requests or other I/O operations take too long to complete.</p>
<p><a href="https://stackoverflow.com/questions/37465816/async-with-in-python-3-4">Here’s an example</a> of how you can define an async with statement with a timeout:</p>
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import asyncio
import aiohttp async def fetch_page(session, url): async with aiohttp.Timeout(10): async with session.get(url) as response: assert response.status == 200 return await response.read()
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<p>This code sets a 10-second timeout to fetch a web page using the <code>aiohttp</code> library.</p>
<h3 class="wp-block-heading">Async With Multiple</h3>
<p>You can use multiple <code>async with</code> statements simultaneously to work with different resources, like file access or database connections. Combining multiple <code>async with</code> statements enables better resource management and cleaner code:</p>
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async def two_resources(resource_a, resource_b): async with aquire_resource_a(resource_a) as a, aquire_resource_b(resource_b) as b: await do_something(a, b)
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<p>This example acquires both resources asynchronously and then performs an operation using them.</p>
<h3 class="wp-block-heading">Async With Lock</h3>
<p>Concurrency can cause issues when multiple tasks access shared resources. To protect these resources and prevent race conditions, you can use <code>async with</code> along with Python’s <code>asyncio.Lock()</code> class:</p>
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import asyncio lock = asyncio.Lock() async def my_function(): async with lock: # Section of code that must be executed atomically.
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<p>This code snippet ensures that the section within the <code>async with</code> block is executed atomically, protecting shared resources from being accessed concurrently.</p>
<h3 class="wp-block-heading">Async With Context Manager</h3>
<p>Creating your own context managers can make it easier to manage resources in asynchronous code. By defining an <code>async def __aenter__()</code> and an <code>async def __aexit__()</code> method in your class, you can use it within an <code>async with</code> statement:</p>
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class AsyncContextManager: async def __aenter__(self): # Code to initialize resource return resource async def __aexit__(self, exc_type, exc, tb): # Code to release resource async def demo(): async with AsyncContextManager() as my_resource: # Code using my_resource
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<p>This custom context manager initializes and releases a resource within the <code>async with</code> block, simplifying your asynchronous code and making it more Pythonic.<img src="https://s.w.org/images/core/emoji/14.0.0/72x72/2728.png" alt="✨" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<h2 class="wp-block-heading">Error Handling and Exceptions</h2>
<figure class="wp-block-image size-full"><img decoding="async" loading="lazy" width="743" height="546" src="https://blog.finxter.com/wp-content/uploads/2023/04/image-234.png" alt="" class="wp-image-1313584" srcset="https://blog.finxter.com/wp-content/uploads/2023/04/image-234.png 743w, https://blog.finxter.com/wp-content/uplo...00x220.png 300w" sizes="(max-width: 743px) 100vw, 743px" /></figure>
<p>When working with <strong>Python’s Async With Statement</strong>, handling errors and exceptions properly is essential to ensure your asynchronous code runs smoothly. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f680.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> Using <a href="https://blog.finxter.com/python-try-except-an-illustrated-guide/" data-type="post" data-id="367118" target="_blank" rel="noreferrer noopener">try-except blocks</a> and well-structured clauses can help you manage errors effectively.</p>
<p>Be aware of syntax errors, which may occur when using async with statements. To avoid SyntaxError, make sure your Python code is properly formatted and follows PEP 343’s guidelines. If you come across an error while performing an IO operation or dealing with external resources, it’s a good idea to handle it with an <code>except</code> clause. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f60e.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p>In the case of exceptions, you might want to apply cleanup code to handle any necessary actions before your program closes or moves on to the next task. One way to do this is by wrapping your <code>async with</code> statement in a try-except block, and then including a <code>finally</code> clause for the cleanup code. </p>
<p>Here’s an example:</p>
<pre class="EnlighterJSRAW" data-enlighter-language="python" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">
try: async with some_resource() as resource: # Perform your IO operation or other tasks here
except YourException as e: # Handle the specific exception here
finally: # Add cleanup code here
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<p>Remember, you need to handle exceptions explicitly in the parent coroutine if you want to prevent them from canceling the entire task. In the case of multiple exceptions or errors, using <code>asyncio.gather</code> can help manage them effectively. <img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4aa.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /></p>
<p class="has-base-2-background-color has-background"><img src="https://s.w.org/images/core/emoji/14.0.0/72x72/1f4a1.png" alt="?" class="wp-smiley" style="height: 1em; max-height: 1em;" /> <strong>Recommended</strong>: <a href="https://blog.finxter.com/python-cheat-sheet/" data-type="post" data-id="305" target="_blank" rel="noreferrer noopener">Python Beginner Cheat Sheet: 19 Keywords Every Coder Must Know</a></p>
</div>
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