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
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
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
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
Summary: Use one of the following methods to format strings that contain curly braces: Use double curly braces {{}} Use the old string formatting, i.e. the % operator Use the JSON Library Use Template Strings Problem: Given a string literal with curly braces; how to format the string and ensure that the curly braces are … Read more
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
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
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
Summary: f-string is more readable and easier to implement than % and .format() string formatting styles. Furthermore, using f-strings is suggested for Python 3.6 and above while .format() is best suited for Python 2.6 and above. Versions prior to Python 2.6 only provide % option for string formatting. In terms of speed, % is the … Read more
To update a global variable in one line of Python, retrieve the global variable dictionary with the globals() function, and access the variable by passing the variable name as a string key such as globals()[‘variable’]. Then overwrite the global variable using the equal symbol, for example in globals()[‘variable’] = 42 to overwrite the variable with … Read more
Summary: To split a string and keep the delimiters/separators you can use one of the following methods: Problem Formulation 🔏Problem: Given a string in Python; how to split the string and also keep the separators/delimiter? A sequence of one or more characters used to separate two or more parts of a given string or a … Read more
Do you hate those lengthy class definitions with __init__ and too many whitespaces and newlines? Python One-Liners to the rescue! Luckily, you can create classes in a single line—and it can even be Pythonic to do so! Sounds too good to be true? Let’s dive right into it! Problem: How to create a Python class … Read more