How to Print a List of List in Python? – Be on the Right Side of Change (original) (raw)
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:
Create the list of lists
lst = [['Alice', 'Data Scientist', '121000'], ['Bob', 'Java Dev', '99000'], ['Ann', 'Python Dev', '111000']]
Find maximal length of all elements in list
n = max(len(x) for l in lst for x in l)
Print the rows
for row in lst: print(''.join(x.ljust(n + 2) for x in row))
I’ll explain this code (and simpler variants) in the following video:
As an exercise, you can also try it yourself in our interactive shell:
Step-By-Step Problem Formulation
Do you want to print a list of lists in Python so that the format doesn’t look like a total mess? In this tutorial, I’ll show you how to orderly print a list of lists in Python—without using any external library.
Before you start to think about the solution, you should understand the problem. What happens if you print a list of lists? Well, let’s try:
lst = [['Alice', 'Data Scientist', 121000], ['Bob', 'Java Dev', 99000], ['Ann', 'Python Dev', 111000]] print(lst)
The output is not very nice:
[['Alice', 'Data Scientist', 121000], ['Bob', 'Java Dev', 99000], ['Ann', 'Python Dev', 111000]]
Instead, you’d would at least want to see a beautiful output like this one where each row has a separate line and the rows are aligned:
[['Alice', 'Data Scientist', 121000], ['Bob', 'Java Dev', 99000], ['Ann', 'Python Dev', 111000]]
And maybe, you even want to see an output that aligns the three columns as well like this one:
Alice Data Scientist 121000
Bob Java Dev 99000
Ann Python Dev 111000
I’ll show you all those different ways of printing a list of lists next. So let’s start with the easiest one:
Print List of Lists With Newline
Problem: Given a list of lists, print it one row per line.
Example: Consider the following example list:
lst = [[1, 2, 3], [4, 5, 6]]
You want to print the list of lists with a newline character after each inner list:
1 2 3 4 5 6
Solution: Use a for loop and a simple print statement:
lst = [[1, 2, 3], [4, 5, 6]]
for x in lst: print(*x)
The output has the desired form:
1 2 3 4 5 6
Explanation: The asterisk operator “unpacks” all values in the inner list x into the print statement. You must know that the print statement also takes multiple inputs and prints them, whitespace-separated, to the shell.
Related articles:
Print List of Lists Without Brackets
To print a list of lists without brackets, use the following code again.
Solution: Use a for loop and a simple print statement:
lst = [[1, 2, 3], [4, 5, 6]]
for x in lst: print(*x)
The output has the desired form:
1 2 3 4 5 6
But how can you print a list of lists by aligning the columns?
Print List of Lists Align Columns
Problem: How to print a list of lists so that the columns are aligned?
Example: Say, you’re going to print the list of lists.
[['Alice', 'Data Scientist', 121000], ['Bob', 'Java Dev', 99000], ['Ann', 'Python Dev', 111000]]
How to align the columns?
Alice 'Data Scientist', 121000], Bob 'Java Dev', 99000], Ann 'Python Dev', 111000]]
Solution: Use the following code snippet to print the list of lists and align all columns (no matter how many characters each string in the list of lists occupies).
Create the list of lists
lst = [['Alice', 'Data Scientist', '121000'], ['Bob', 'Java Dev', '99000'], ['Ann', 'Python Dev', '111000']]
Find maximal length of all elements in list
n = max(len(x) for l in lst for x in l)
Print the rows
for row in lst: print(''.join(x.ljust(n + 2) for x in row))
The output is the desired:
Alice Data Scientist 121000
Bob Java Dev 99000
Ann Python Dev 111000
Explanation:
- First, you determine the length
n(in characters) of the largest string in the list of lists using the statementmax(len(x) for l in lst for x in l). The code uses a nested for loop in a generator expression to achieve this. - Second, you iterate over each list in the list of lists (called
row). - Third, you create a string representation with columns aligned by ‘padding’ each row element so that it occupies
n+2characters of space. The missing characters are filled with empty spaces.
You can see the code in action in the following memory visualizer. Just click “Next” to see which objects are created in memory if you run the code in Python:
Related articles: You may need to refresh your understanding of the following Python features used in the code:
Print List of Lists with Pandas
Last but not least, I’ll show you my simple favorite: simply import the pandas library (the excel of Python coders) and print the DataFrame. Pandas takes care of pretty formatting:
lst = [['Alice', 'Data Scientist', '121000'], ['Bob', 'Java Dev', '99000'], ['Ann', 'Python Dev', '111000']]
import pandas as pd df = pd.DataFrame(lst) print(df)
The output looks beautiful—like a spreadsheet in your Python shell:
0 1 20 Alice Data Scientist 121000 1 Bob Java Dev 99000 2 Ann Python Dev 111000
Where to Go From Here?
Enough theory. Let’s get some practice!
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