Many Python coders—even at intermediate skill levels—are often puzzled when it comes to the asterisk character in Python. What does it mean? How does it work? What’s it purpose? This article answers all of those questions and more. After studying this article, you will have a solid understanding of the asterisk operator * in Python—and … Read more
This interesting code snippet was brought to my attention by Finxter reader Albrecht. You’d guess that the for loop goes from i=250 to i=259, each time incrementing a and b. As Python creates one integer object to which both names refer, the command a is not b should always be False. Thus, the result is … Read more
To break one line into multiple lines in Python, use an opening parenthesis in the line you want to break. Now, Python expects the closing parenthesis in one of the next lines and the expression is evaluated across line boundaries. As an alternative, you can also use the backslash \ just in front of the … Read more
Problem: Given the contents of a text file. How to search and replace a specific string or line in the file? Example: Let’s consider the following example where you want to replace the highlighted (bolded) text parts. Text in the file before replacing a line: There was an idea to bring together a group of … 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
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
Problem: Given a string and a filename. How to write the string into the file with filename using only a single line of Python code? Example: You have filename ‘hello.txt’ and you want to write string ‘hello world!’ into the file. How to achieve this? In this tutorial, you’ll learn four ways of doing it … Read more
This is a running document in which I’ll answer all questions regarding the single line of Python code. If you want to become a one-liner wizard, check out my book “Python One-Liners”! 🙂 This document contains many interactive code shells and videos to help you with your understanding. However, it’s pretty slow because of all … Read more
Problem: Given are two lists l1 and l2. You want to perform either of the following: 1. Boolean Comparison: Compare the lists element-wise and return True if your comparison metric returns True for all pairs of elements, and otherwise False. 2. Difference: Find the difference of elements in the first list but not in the … Read more
The standard way of checking if an element exists in a list is to use the in keyword. For example, ‘Alice’ in [1, ‘Alice’, 3] will return True while the same returns False for ‘Bob’. If you need to check more complicated conditions, use the any(condition(x) for x in list) function with a generator expression. … Read more
To convert a list lst of strings to a string, use the ”.join(lst) method with an empty separator string between the elements. If you have a list of objects, first convert each element to a string and join the result with the generator expression ”.join(str(x) for x in lst). Problem: Given a list of elements. … Read more