To test multiple variables x, y, z against a value in Python, use the expression value in {x, y, z}. Checking membership in a set has constant runtime complexity. Thus, this is the most efficient way to test multiple variables against a value. Here’s the code: Exercise: Add a fourth variable and run the modified … Read more
Python cheat sheets are the 80/20 principle applied to coding: learn 80% of the language features in 20% of the time.Download and pin this cheat sheet to your wall until you feel confident using all these tricks. Download PDF for Printing Try It Yourself: Exercise: Modify each function and play with the output! Here’s 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
Answer: The simplest, most straightforward, and most readable way to convert a list to a tuple is Python’s built-in tuple(list) function. You can pass any iterable (such as a list, another tuple, or a set) as an argument into this so-called constructor function and it returns a new tuple data structure that contains all elements … 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
The method os.path.exists(‘file.txt’) returns True if the file ‘file.txt’ exists, and False otherwise. To use it, import the os module first with import os. If you want to check if a file exists at a given path, use the standard path notation ‘/file/at/path/file.txt’ as a prefix. The web is full of guides that show you … Read more
If you’re like me, you may have asked yourself the following question: Why is it string.join(list) instead of list.join(string) in Python? ? The join method works with any iterable, not just with lists. Therefore, you’d have to implement it in hundreds of classes instead of just one (in the string class). Additionally, join() works only … Read more
Call random.shuffle(list) to randomize the order of the elements in the list after importing the random module with import random. This shuffles the list in place. If you need to create a new list with shuffled elements and leave the original one unchanged, use slicing list[:] to copy the list and call the shuffle function … Read more
The most Pythonic way to concatenate a list of objects is the expression ”.join(str(x) for x in lst) that converts each object to a string using the built-in str(…) function in a generator expression. You can concatenate the resulting list of strings using the join() method on the empty string as a delimiter. The result … Read more
To extract elements with specific indices from a Python list, use slicing list[start:stop:step]. If you cannot use slicing because there’s no pattern in the indices you want to access, use the list comprehension statement [lst[i] for i in indices], assuming your indices are stored in the variable indices. People always want to know the most … Read more
To convert a Python list to a NumPy array, use either of the following two methods: Exercise: Create array b from array a using both methods. Then change a value in array a. What happens at array b? NumPy vs Python Lists The Python built-in list data type is powerful. However, the NumPy array has … Read more
Q: What’s the object-oriented way to become wealthy? A: Inheritance. ? Your vocabulary determines the reality of your life. In this tutorial, I have compiled the most essential terms and concepts of object-oriented programming in Python. My goal was to create the best Python OOP cheat sheet that shows them in one place. Well — … Read more