To check if two unordered lists x and y are identical, compare the converted sets with set(x) == set(y). However, this loses all information about duplicated elements. To consider duplicates, compare the sorted lists with sorted(x) == sorted(y). Due to the efficient merge-sort-like implementation of the sorted() function, this is quite fast for almost-sorted lists. … Read more
The most Pythonic way to check if two ordered lists l1 and l2 are identical, is to use the l1 == l2 operator for element-wise comparison. If all elements are equal and the length of the lists are the same, the return value is True. Problem: Given are two lists l1 and l2. You want … Read more
Answer: The simplest, most straightforward, and most readable way to convert a tuple to a list is Python’s built-in list(tuple) function. You can pass any iterable (such as a tuple, another list, or a set) as an argument into this so-called constructor function and it returns a new list data structure that contains all elements … Read more
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
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
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
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 join a list of DataFrames, say dfs, use the pandas.concat(dfs) function that merges an arbitrary number of DataFrames to a single one. When browsing StackOverflow, I recently stumbled upon the following interesting problem. By thinking about solutions to those small data science problems, you can improve your data science skills, so let’s dive into … 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