ChrisProblem: You have a list of lists and you want to calculate the average of the different columns. Example: Given the following list of lists with four rows and three columns. You want to have the average values of the three columns: There are three methods that solve this problem. You can play with them … Read more
What’s the best way to remove duplicates from a Python list of lists? This is a popular coding interview question at Google, Facebook, and Amazon. In this article, I’ll show you how (and why) it works—so keep reading! How to remove all duplicates of a given value in the list? Method 1: Naive Method Algorithm: … Read more
Short answer: You can remove all empty lists from a list of lists by using the list comprehension statement [x for x in list if x] to filter the list. In the following, you’ll learn about the two methods using list comprehension and the filter() function to remove all empty lists from a list of … Read more
Short answer: To print a list of lists in Python without brackets and aligned columns, use the ”.join() function and a generator expression to fill each string with enough whitespaces so that the columns align: I’ll explain this code (and simpler variants) in the following video: As an exercise, you can also try it yourself … Read more
[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
You can convert a list of lists to a Pandas DataFrame that provides you with powerful capabilities such as the to_csv() method. This is the easiest method and it allows you to avoid importing yet another library (I use Pandas in many Python projects anyways). Output: # file2.csv Alice,Data Scientist,122000 Bob,Engineer,77000 Ann,Manager,119000 You create a … 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
Short answer: Convert a list of lists—let’s call it l—to a NumPy array by using the standard np.array(l) function. This works even if the inner lists have a different number of elements. Convert List of Lists to 2D Array Problem: Given a list of lists in Python. How to convert it to a 2D NumPy … Read more
For some applications, it’s quite useful to convert a list of lists into a dictionary. Databases: List of list is table where the inner lists are the database rows and you want to assign each row to a primary key in a new dictionary. Spreadsheet: List of list is two-dimensional spreadsheet data and you want … 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