[Tut] Python One Line X - Printable Version

[Tut] Python One Line X - Printable Version

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[Tut] Python One Line X - xSicKxBot - 07-13-2020

Python One Line X

This is a running document in which I’ll answer all questions regarding the single line of Python code. If you want to check out my book “Python One-Liners” and become a one-liner wizard—be my guest!

Let’s get started!

Python One Line If Without Else

Python One Line If Else

Python One Line Elif

Python One Line Function

Python One Line For Loop

Python One Line For Loop If

Python One Line For Loop Lambda

Python One Line While Loop

Python One Line HTTP Web Server

Want to create your own webserver in a single line of Python code? No problem, just use this command in your shell:

[Image: image-61.png]

Code:
$ python -m http.server 8000

The terminal will tell you:

Code:
Serving HTTP on 0.0.0.0 port 8000

To shut down your webserver, kill the Python program with

Code:
CTRL+c

.

This works if you’ve Python 3 installed on your system. To check your version, use the command

Code:
python --version

in your shell.

You can run this command in your Windows Powershell, Win Command Line, MacOS Terminal, or Linux Bash Script.

You can see in the screenshot that the server runs on your local host listening on port 8000 (the standard HTTP port to serve web requests).

Note: The IP address is NOT 0.0.0.0—this is an often-confused mistake by many readers. Instead, your webserver listens at your “local” IP address 127.0.0.1 on port 8000. Thus, only web requests issued on your computer will arrive at this port. The webserver is NOT visible to the outside world.

Python 2: To run the same simple webserver on Python 2, you need to use another command using

Code:
SimpleHTTPServer

instead of

Code:
http

Code:
$ python -m SimpleHTTPServer 8000
Serving HTTP on 0.0.0.0 port 8000 ...

If you want to start your webserver from within your Python script, no problem:

Code:
import http.server
import socketserver PORT = 8000 Handler = http.server.SimpleHTTPRequestHandler with socketserver.TCPServer(("", PORT), Handler) as httpd: print("serving at port", PORT) httpd.serve_forever()

You can execute this in our online Python browser (yes, you’re creating a local webserver in the browser—how cool is that)!

https://repl.it/@finxter/webserver?lite=true

This code comes from the official Python documentation—feel free to read more if you’re interested in setting up the server (most of the code is relatively self-explanatory).

Source: Python One-Liner Webserver HTTP

Python One Line Webshell

Python One Line Write String to File

Python One Line Quine

Python One Line Quicksort

In this one-liner tutorial, you’ll learn about the popular sorting algorithm Quicksort. Surprisingly, a single line of Python code is all you need to write the Quicksort algorithm!

Problem: Given a list of numerical values (integer or float). Sort the list in a single line of Python code using the popular Quicksortalgorithm!

Example: You have list

Code:
[4, 2, 1, 42, 3]

. You want to sort the list in ascending order to obtain the new list

Code:
[1, 2, 3, 4, 42]

.

Short answer: The following one-liner solution sorts the list recursively using the Quicksort algorithm:

Code:
q = lambda l: q([x for x in l[1:] if x <= l[0]]) + [l[0]] + q([x for x in l if x > l[0]]) if l else []

You can try it yourself using the following interactive code shell:

https://trinket.io/embed/python/82f77b2571

Now, let’s dive into some details!

The following introduction is based on my new book “Python One-Liners” (Amazon Link) that teaches you the power of the single line of code (use it wisely)!

Introduction: Quicksortis not only a popular question in many code interviews – asked by Google, Facebook, and Amazon – but also a practical sortingalgorithm that is fast, concise, and readable. Because of its beauty, you won’t find many introduction to algorithm classes which don’t discuss the Quicksort algorithm.

Overview: Quicksort sorts a list by recursivelydividing the big problem (sorting the list) into smaller problems (sorting two smaller lists) and combining the solutions from the smaller problems in a way that it solves the big problem. In order to solve each smaller problem, the same strategy is used recursively: the smaller problems are divided into even smaller subproblems, solved separately, and combined. Because of this strategy, Quicksort belongs to the class of “Divide and Conquer” algorithms.

Algorithm: The main idea of Quicksort is to select a pivot element and then placing all elements that are larger or equal than the pivot element to the right and all elements that are smaller than the pivot element to the left. Now, you have divided the big problem of sorting the list into two smaller subproblems: sorting the right and the left partition of the list. What you do now is to repeat this procedure recursively until you obtain a list with zero elements. This list is already sorted, so the recursion terminates.

The following Figure shows the Quicksort algorithm in action:

[Image: image-11.png]

Figure: The Quicksort algorithm selects a pivot element, splits up the list into (i) an unsorted sublist with all elements that are smaller or equal than the pivot, and (ii) an unsorted sublist with all elements that are larger than the pivot. Next, the Quicksort algorithm is called recursively on the two unsorted sublists to sort them. As soon as the sublists contain maximally one element, they are sorted by definition – the recursion ends. At every recursion level, the three sublists (left, pivot, right) are concatenated before the resulting list is handed to the higher recursion level.

You create a function

Code:
q

which implements the Quicksort algorithm in a single line of Python code – and thus sorts any argument given as a list of integers.

Code:
## The Data
unsorted = [33, 2, 3, 45, 6, 54, 33] ## The One-Liner
q = lambda l: q([x for x in l[1:] if x <= l[0]]) + [l[0]] + q([x for x in l if x > l[0]]) if l else [] ## The Result
print(q(unsorted))

What is the output of this code?

Code:
## The Result
print(q(unsorted))
# [2, 3, 6, 33, 33, 45, 54]

Python One Line With Statement

Python One Line Exception Handling

Python One Line Try Except

Python One Line Execute

Python One Line Reverse Shell

Python One Line Read File

Python One Line Return If

Python One Line Regex Match

Python One Line Recursion

Python One Line Regex

Python One Line Read File to List

Python One Line Read Stdin

Python One Line Replace

Python One Line Ternary

Ternary (from Latin ternarius) is an adjective meaning “composed of three items”. (source) So, literally, the ternary operator in Python is composed of three operands.

Syntax: The three operands are written in an intuitive combination

Code:
... if ... else ...

Code:
<On True> if <Condition> else <On False>

Operand |
Description

<On True> |
The return expression of the operator in case the condition evaluates to

Code:
True

<Condition> |
The condition that determines whether to return the <On True> or the <On False> branch.

<On False> |
The return expression of the operator in case the condition evaluates to

Code:
False

[i]Operands of the Ternary Operator[/i]

Let’s have a look at a minimum example in our interactive code shell:

https://trinket.io/embed/python/42f3df6ddd

Exercise: Run the code and input your age. What’s the output? Run the code again and try to change the output!

Python One Line Two For Loops

Python One Line True False

Python One Line Too Long

Python One Line Two Commands

Python One Line To Multiple Line

Python One Line URL Decode

Python One Line Or

Python One Line Object

Python One Line Open File

Python One Line Print

Python One Line Print For Loop

Python One Line Print If

Python One Line Print List

Python One Line Parse JSON

Python One Line Pretty Print JSON

Python One Line Array Filter

Python One Line Append

Python One Line And Or

Python One Line Conditional Assignment

Python One Swap

Python One Line Sum

Python One Line Sort

Python One Line Semicolon

Python One Line Dictionary

Python One Line Function Definition

Python One Line Def

Python One Line Docstring

Python One Line Dict Comprehension

Python One Line Double For Loop

Python One Line Download File

Python One Line For Loop Append

Python One Line Generator

Python One Line FizzBuzz

Python One Line HTTP Get

Python Global in One Line

Python One Line Hello World

Python One Line Comment

Python One Line Class

Python Define Two Variables in One Line

Python Define Multiple Variables in One Line

Python One Line If (Not) None

Python One Line Map