[20-SEC SUMMARY] Given a list of list stored in variable lst. To flatten a list of lists, use the list comprehension statement [x for l in lst for x in l]. To modify all elements in a list of lists (e.g., increment them by one), use a list comprehension of list comprehensions [[x+1 for x … Read more
Pandas is an open-source Python library that is powerful and flexible for data analysis. If there is something you want to do with data, the chances are it will be possible in pandas. There are a vast number of possibilities within pandas, but most users find themselves using the same methods time after time. In this … Read more
If you’re in a hurry, here’s the short answer: Use the list comprehension statement [list(x) for x in tuples] to convert each tuple in tuples to a list. This also works for a list of tuples with a varying number of elements. But there’s more to it, and studying the three main methods to achieve … Read more
If you’re in a hurry, here’s the short answer: use the list comprehension statement [tuple(x) for x in list] to convert each element in your list to a tuple. This works also for list of lists with varying number of elements. But there’s more to it and studying the two main methods to achieve the … Read more
Problem: You’re given a list of lists. Your goal is to convert it into a Pandas Dataframe. Example: Say, you want to compare salary data of different companies and job descriptions. You’ve obtained the following salary data set as a list of list: How can you convert this into a Pandas Dataframe? DataFrame() Solution: The … Read more
Say, you want to convert a list of lists lst=[[1, 2], [3, 4]] into a single list [1, 2, 3, 4]. How to achieve this? There are different options: List comprehension [x for l in lst for x in l] assuming you have a list of lists lst. Unpacking [*lst[0], *lst[1]] assuming you have a … Read more
Summing up a list of numbers appears everywhere in coding. Fortunately, Python provides the built-in sum() function to sum over all elements in a Python list—or any other iterable for that matter. (Official Docs) The syntax is sum(iterable, start=0): Argument Description iterable Sum over all elements in the iterable. This can be a list, a … Read more
[Spoiler] Which function filters a list faster: filter() vs list comprehension? For large lists with one million elements, filtering lists with list comprehension is 40% faster than the built-in filter() method. To answer this question, I’ve written a short script that tests the runtime performance of filtering large lists of increasing sizes using the filter() … Read more
How can you filter a list in Python using an arbitrary condition? The most Pythonic and most performant way is to use list comprehension [x for x in list if condition] to filter all elements from a list. Filter with List Comprehension The most Pythonic way of filtering a list—in my opinion—is the list comprehension … Read more
In this article, you’ll learn how to filter a list of dictionaries. So let’s get started! Short answer: The list comprehension statement [x for x in lst if condition(x)] creates a new list of dictionaries that meet the condition. All dictionaries in lst that don’t meet the condition are filtered out. You can define your … Read more
Want to convert two lists into a dictionary? Do the following: Zip the lists together using zip(list_1, list_2). Create a dictionary from the list of tuples using the constructor dict() on the result. In other words, call dict(zip(list_1, list_2)) to convert two lists into a dictionary. Try it yourself: Let’s dive into the code step-by-step. … Read more
Want to calculate the standard deviation of a column in your Pandas DataFrame? In case you’ve attended your last statistics course a few years ago, let’s quickly recap the definition of variance: it’s the average squared deviation of the list elements from the average value. You can do this by using the pd.std() function that … Read more