[Tut] Python List to String: A Helpful Guide with Interactive Shell

[Tut] Python List to String: A Helpful Guide with Interactive Shell - Printable Version

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[Tut] Python List to String: A Helpful Guide with Interactive Shell - xSicKxBot - 04-18-2020

Python List to String: A Helpful Guide with Interactive Shell

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<div class="ast-oembed-container"><iframe title="Python List to String: A Helpful Guide" width="1400" height="788" src="https://www.youtube.com/embed/2DaXCB1gusI?feature=oembed" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
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Problem: Given a list of strings. How to convert the list to a string by <a href="https://blog.finxter.com/concatenate-lists-in-python/" target="_blank" rel="noreferrer noopener">concatenating</a> all strings in the list?
Example: You want to convert list <code>['learn ', 'python ', 'fast']</code> to the string <code>'learn python fast'</code>. 
Solution: to convert a list of strings to a string, do the following.
<ul>
<li>Call the <code>''.join(list)</code> method on the empty string <code>''</code> that glues together all strings in the <code>list</code> and returns a new string. </li>
<li>The string on which you call the join method is used as a delimiter between the list elements. </li>
<li>If you don’t need a delimiter, just use the empty string <code>''</code>. </li>
</ul>
Code: Let’s have a look at the code.
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn ', 'python ', 'fast']
print(''.join(lst))</pre>
The output is:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">learn python fast</pre>
Try it yourself in our interactive Python shell:
 <iframe height="400px" width="100%" src="https://repl.it/@finxter/joinpythonstringlist?lite=true" scrolling="no" frameborder="no" allowtransparency="true" allowfullscreen="true" sandbox="allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-modals"></iframe> 
You can also use another delimiter string, for example, the comma:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn' , 'python', 'fast']
print(','.join(lst))
# learn,python,fast</pre>
<h2>What Are Alternative Methods to Convert a List of Strings to a String?</h2>
Python is flexible—you can use multiple methods to achieve the same thing. So what are the different methods to convert a list to a string?
<ul>
<li>Method 1: Use the method <code>''.join(list)</code> to concatenate all strings in a given list to a single list. The string on which you call the method is the delimiter between the list elements. </li>
<li>Method 2: Start with an empty string variable. Use a simple for loop to iterate over all elements in the list and add the current element to the string variable.</li>
<li>Method 3: Use <a rel="noreferrer noopener" href="https://blog.finxter.com/list-comprehension/" target="_blank">list comprehension</a> <code>[str(x) for x in list]</code> if the list contains elements of different types to convert all elements to the string data type. Combine them using the <code>''.join(newlist)</code> method. </li>
<li>Method 4: Use the <a rel="noreferrer noopener" href="https://blog.finxter.com/daily-python-puzzle-string-encrpytion-ord-function-map-function/" target="_blank">map function</a> <code>map(str, list]</code> if the list contains elements of different types to convert all elements to the string data type. Combine them using the <code>''.join(newlist)</code> method.</li>
</ul>
Here are all four variants in some code:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn' , 'python', 'fast'] # Method 1
print(''.join(lst))
# learnpythonfast # Method 2
s = ''
for st in lst: s += st
print(s)
# learnpythonfast # Method 3
lst = ['learn', 9, 'python', 9, 'fast']
s = ''.join([str(x) for x in lst])
print(s)
# learn9python9fast # Method 4
lst = ['learn', 9, 'python', 9, 'fast']
s = ''.join(map(str, lst))
print(s)
# learn9python9fast
</pre>
Again, try to modify the delimiter string yourself using our interactive code shell:
 <iframe height="800px" width="100%" src="https://repl.it/@finxter/listtostring?lite=true" scrolling="no" frameborder="no" allowtransparency="true" allowfullscreen="true" sandbox="allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-modals"></iframe> 
So far so good. You’ve learned how to convert a list to a string. But that’s not all! Let’s dive into some more specifics of converting a list to a string. 
<h2>Python List to String with Commas</h2>
Problem: Given a list of strings. How to convert the list to a string by <a rel="noreferrer noopener" href="https://blog.finxter.com/concatenate-lists-in-python/" target="_blank">concatenating</a> all strings in the list—using a comma as the delimiter between the list elements?
Example: You want to convert list <code>['learn', 'python', 'fast']</code> to the string <code>'learn,python,fast'</code>. 
Solution: to convert a list of strings to a string, call the <code>','.join(list)</code> method on the delimiter string <code>','</code> that glues together all strings in the <code>list</code> and returns a new string. 
Code: Let’s have a look at the code.
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn', 'python', 'fast']
print(','.join(lst))</pre>
The output is:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">learn,python,fast</pre>
<h2>Python List to String with Spaces</h2>
Problem: Given a list of strings. How to convert the list to a string by <a rel="noreferrer noopener" href="https://blog.finxter.com/concatenate-lists-in-python/" target="_blank">concatenating</a> all strings in the list—using a space as the delimiter between the list elements?
Example: You want to convert list <code>['learn', 'python', 'fast']</code> to the string <code>'learn python fast'</code>. (Note the empty spaces between the terms.)
Solution: to convert a list of strings to a string, call the <code>' '.join(list)</code> method on the string <code>' '</code> (space character) that glues together all strings in the <code>list</code> and returns a new string. 
Code: Let’s have a look at the code.
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn', 'python', 'fast']
print(' '.join(lst))</pre>
The output is:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">learn python fast</pre>
<h2>Python List to String with Newlines</h2>
Problem: Given a list of strings. How to convert the list to a string by <a rel="noreferrer noopener" href="https://blog.finxter.com/concatenate-lists-in-python/" target="_blank">concatenating</a> all strings in the list—using a newline character as the delimiter between the list elements?
Example: You want to convert list <code>['learn', 'python', 'fast']</code> to the string <code>'learn\npython\nfast'</code> or as a multiline string:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">'''learn
python
fast'''</pre>
Solution: to convert a list of strings to a string, call the <code>'\n'.join(list)</code> method on the newline character <code>'\n'</code> that glues together all strings in the <code>list</code> and returns a new string. 
Code: Let’s have a look at the code.
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn', 'python', 'fast']
print('\n'.join(lst))</pre>
The output is:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">learn
python
fast</pre>
<h2>Python List to String with Quotes</h2>
Problem: Given a list of strings. How to convert the list to a string by <a rel="noreferrer noopener" href="https://blog.finxter.com/concatenate-lists-in-python/" target="_blank">concatenating</a> all strings in the list—using a comma character followed by an empty space as the delimiter between the list elements? Additionally, you want to wrap each string in double quotes.
Example: You want to convert list <code>['learn', 'python', 'fast']</code> to the string <code>'"learn", "python", "fast"'</code> :
Solution: to convert a list of strings to a string, call the <code>', '.join('"' + x + '"' for x in lst)</code> method on the delimiter string <code>', '</code> that glues together all strings in the <code>list</code> and returns a new string. You use a generator expression to modify each element of the original element so that it is enclosed by the double quote <code>"</code> chararacter. 
Code: Let’s have a look at the code.
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn', 'python', 'fast']
print(', '.join('"' + x + '"' for x in lst))
</pre>
The output is:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">"learn", "python", "fast"</pre>
<h2>Python List to String with Brackets</h2>
Problem: Given a list of strings. How to convert the list to a string by <a rel="noreferrer noopener" href="https://blog.finxter.com/concatenate-lists-in-python/" target="_blank">concatenating</a> all strings in the list—using a comma character followed by an empty space as the delimiter between the list elements? Additionally, you want to wrap the whole string in a square bracket to indicate that’s a list.
Example: You want to convert list <code>['learn', 'python', 'fast']</code> to the string <code>'[learn, python, fast]'</code> :
Solution: to convert a list of strings to a string, call the <code>'[' + ', '.join(lst) + ']'</code> method on the delimiter string <code>', '</code> that glues together all strings in the <code>list</code> and returns a new string.
Code: Let’s have a look at the code.
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn', 'python', 'fast']
print('[' + ', '.join(lst) + ']')
</pre>
The output is:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">[learn, python, fast]</pre>
<h2>Python List to String and Back</h2>
Problem: You want to convert a list into a string and back to a list.
Example: Convert the list <code>['learn', 'python', 'fast']</code> to a string <code>"['learn', 'python', 'fast']"</code> and back to a list <code>['learn', 'python', 'fast']</code>. 
Solution: Use the following two steps to convert back and forth between a string and a list:
<ul>
<li>Use the built-in <code>str()</code> function to convert from a list to a string.</li>
<li>Use the built-in <code>eval()</code> function to convert from a string to a list.</li>
</ul>
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['learn', 'python', 'fast'] converted = str(lst)
print(converted)
# ['learn', 'python', 'fast']
print(type(converted))
# <class 'str'> original = eval(converted)
print(original)
# ['learn', 'python', 'fast']
print(type(original))
# <class 'list'></pre>
Although the output of both the converted list and the original list look the same, you can see that the data type is <code>string</code> for the former and <code>list</code> for the latter. 
<h2>Convert List of Int to String</h2>
Problem: You want to convert a list into a string but the list contains integer values.
Example: Convert the list <code>[1, 2, 3]</code> to a string <code>'123'</code>.
Solution: Use the join method in combination with a <a href="https://blog.finxter.com/list-comprehension/" target="_blank" rel="noreferrer noopener">generator expression</a> to convert the list of integers to a single string value: 
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = [1, 2, 3]
print(''.join(str(x) for x in lst))
# 123</pre>
The generator expression converts each element in the list to a string. You can then combine the string elements using the join method of the string object. 
If you miss the conversion from integer to string, you get the following <code>TypeError</code>:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = [1, 2, 3]
print(''.join(lst)) '''
Traceback (most recent call last): File "C:\Users\xcent\Desktop\code.py", line 2, in <module> print(''.join(lst))
TypeError: sequence item 0: expected str instance, int found '''</pre>
<h2>Python List to String One Line</h2>
To convert a list to a string in one line, use either of the three methods:
<ul>
<li>Use the <code>''.join(list)</code> method to glue together all list elements to a single string.</li>
<li>Use the list comprehension method <code>[str(x) for x in lst]</code> to convert all list elements to type string. </li>
<li>Use <code>str(list)</code> to convert the list to a string representation.</li>
</ul>
Here are three examples:
<pre class="EnlighterJSRAW" data-enlighter-language="generic" data-enlighter-theme="" data-enlighter-highlight="" data-enlighter-linenumbers="" data-enlighter-lineoffset="" data-enlighter-title="" data-enlighter-group="">lst = ['finxter', 'is', 'awesome']
print(' '.join(lst))
# finxter is awesome lst = [1, 2, 3]
print([str(x) for x in lst])
# ['1', '2', '3'] print(str(lst))
# [1, 2, 3]</pre>
<h2>Where to Go From Here</h2>
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