Problem: Given multiple Python statements. How to write them as a Python One-Liner? Example: Consider the following example of four statements in a block with uniform indentation: Each of the four statements is written in a separate line in a code editor—this is the normal procedure. However, what if you want to one-linerize those: How … Read more
Summary: To write a nested for loop in a single line of Python code, use the one-liner code [print(x, y) for x in iter1 for y in iter2] that iterates over all values x in the first iterable and all values y in the second iterable. Problem: How to write a nested for loop as … Read more
Problem: You use Python in a terminal and you want to replace a string ‘example’ in a text file file.txt: Your goal is to accomplish the following text: In particular, you want to open the file, replace the text, and rewrite the result into the file—all in a single line of Python code! Can a … Read more
Summary: To match a pattern in a given text using only a single line of Python code, use the one-liner import re; print(re.findall(pattern, text)) that imports the regular expression library re and prints the result of the findall() function to the shell. Problem: Given a string and a regular expression pattern. Match the string for … Read more
Two ways of writing a recursive one-liner: (1) write the function with return statement in a single line such as in def f(x): return f(x+1), or (2) assign a lambda function to a variable name and use the variable name in the return expression of the lambda function such as in f = lambda x: … Read more
Problem: How to return from a Python function or method in single line? Example: Consider the following “goal” statement: However, this leads to a Syntax error: In this tutorial, you’ll learn how to write the return statement with an if expression in a single line of Python code. You can get an overview of the … Read more
Summary: To make a Python one-liner out of any multi-line Python script, replace the new lines with a new line character ‘\n’ and pass the result into the exec(…) function. You can run this script from the outside (command line, shell, terminal) by using the command python -c “exec(…)”. Problem: Given a multi-line code script … Read more
Summary: You can accomplish one line exception handling with the exec() workaround by passing the one-linerized try/except block as a string into the function like this: exec(‘try:print(x)\nexcept:print(“Exception!”)’). This general method works for all custom, even multi-line, try and except blocks. However, you should avoid this one-liner code due to the bad readability. Surprisingly, there has … Read more
The with statement replaces former try…finally blocks in Python. It ensures that clean-up code is executed. For example, it closes open files before leaving the block. Consider this code example (assuming this code is stored in a file named ‘code.py’): The output of this code would be the code itself (for nerds: a piece of … Read more
Most computer scientists, programmers, and hackers don’t even know the meaning of the word “Quine” in the context of programming. So, first things first: What is a Quine? Roughly speaking, a quine is a self-reproducing program: if you run it, it generates itself. Here’s a great definition: :quine: /kwi:n/ /n./ [from the name of the … Read more
Python is powerful — you can condense many algorithms into a single line of Python code. So the natural question arises: can you write a while loop in a single line of code? This article explores this mission-critical question in all detail. How to Write a While Loop in a Single Line of Python Code? … Read more
Problem: Given a collection. You want to create a new list based on all values in this collection. The code should run in a single line of code. How do you accomplish this? Do you need a lambda function? Example: Given an array a = [1, 2, 3, 4]. You need to create a second … Read more