Python Reverse List with Slicing — An Illustrated Guide

Summary: The slice notation list[::-1] with default start and stop indices and negative step size -1 reverses a given list. Problem: Given a list of elements. How to reverse the order of the elements in the list. Example: Say, you’ve got the following list: Your goal is to reverse the elements to obtain the following … Read more

How to Remove Duplicates From a Python List While Preserving Order?

To remove duplicates from a Python list while preserving the order of the elements, use the code list(dict.fromkeys(list)) that goes through two phases: (1) Convert the list to a dict using the dict.fromkeys() function with the list elements as keys and None as dict values. (2) Convert the dictionary back to a list using the … Read more

How to Get the Last Element of a Python List?

Problem: Given a list. How to access the last element of this list? Example: You have the list [‘Alice’, ‘Bob’, ‘Liz’] and you want to get the last element ‘Liz’. Quick solution: Use negative indexing -1. To access the last element of a Python list, use the indexing notation list[-1] with negative index -1 which … Read more

List Changes After Assignment — How to Clone or Copy It?

Problem: If you assign a list object to a new variable using new_list = old_list, any modification to new_list changes old_list. What’s the reason for this and how can you clone or copy the list to prevent this problem? Example: Let’s consider the following example. Appending an element to the new_list also modifies the original … Read more

Python One Line Dictionary

Python’s dictionary data structure is one of the most powerful, most underutilized data structures in Python. Why? Because checking membership is more efficient for dictionaries than for lists, while accessing elements is easier for dictionaries than for sets. In this tutorial, you’ll learn how to perform four common dictionary operations in one line of Python … Read more

Python Unicode Encode Error

Summary: The UnicodeEncodeError generally occurs while encoding a Unicode string into a certain coding. Only a limited number of Unicode characters are mapped to strings. Thus, any character that is not-represented / mapped will cause the encoding to fail and raise UnicodeEncodeError. To avoid this error use the encode(utf-8) and decode(utf-8) functions accordingly in your … Read more

[Dash + Flask] How to Deploy a Python Dash App on Pythonanywhere.com

Here’s the step-by-step approach of how to deploy your Dash app on Pythonanywhere.com using Flask and pip: Create an account on Pythonanywhere.com. Create a Flask application. Create a Dash application. Copy the Dash app into the Flask app. Connect the Flask server with the Dash app. Modify the WSGI configuration file. Install Dash with pip … Read more

Python One-Line Password Generator

Can you believe it? People use unknown and potentially insecure websites to generate their random passwords! This works as follows: A website generates a “random” password for them and they copy&paste it and assume this is a safe password because of the randomness of the characters. What a security flaw! Why? Because the website could … Read more

How to Solve Python “TypeError: ‘int’ object is not iterable”?

It’s quite common for your code to throw a typeerror, especially if you’re just starting out with Python. The reason for this is that the interpreter expects variables of certain types in certain places in the code. We’ll look at a specific example of such an error: “typeerror: ‘int’ object is not iterable”. Exercise: Run … Read more

Calculating Entropy with SciPy

Problem: How to calculate the entropy with the SciPy library? Solution: Import the entropy() function from the scipy.stats module and pass the probability and the base of the logarithm into it. Try It Yourself: Run this code in the interactive code shell! Exercise: Change the probabilities. How does the entropy change? Let’s start slowly! You’ll … Read more