Add Comma Between Numbers - Python

Last Updated : 17 Jan, 2025

When working with large numbers in Python, adding commas for better readability can make them easier to understand. In this article, we’ll explore simple ways to add commas between numbers, helping make large numbers more readable and neatly formatted.

Using format()

format() function in Python provides a simple and efficient way to add commas between numbers.

Python

n = 1000000 res = "{:,}".format(n) print(res)

Output

1,000,000

Explanation:

format() function is used to format the number and add commas.
The :, within the curly braces tells Python to insert commas as a thousand separator.

Let's explore some more ways and see how we can add commas between numbers.

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Using f-strings

f-strings provide an even more convenient way to add commas to numbers. This method provides a quick way to format numbers.

Python

n = 1000000 res = f"{n:,}" print(res)

Output

1,000,000

Explanation:

f-strings allow us to embed expressions directly inside string literals.
The :, is used to format the number with commas as a thousand separator.
This method is more readable and concise compared to using str.format()

Using locale module

locale module allows us to format numbers according to the conventions of a specific locale. This is useful if we need to format numbers in a way that’s specific to certain countries or regions.

Python

import locale  # Setting the locale to 'en_US' for formatting numbers with commas (US-style) locale.setlocale(locale.LC_ALL, "en_US") n = 1000000  # Using the locale module to format the number with commas as thousand separators res = locale.format_string("%d", n, grouping=True) print(res)

Explanation:

setlocale() function sets the locale for formatting numbers.
format_string function is used to format the number with commas based on the locale.
This method is ideal when dealing with international number formatting requirements.

Using str.replace() with a loop

Another approach is to manually insert commas using str.replace() and a loop. This method can still be used for smaller tasks or custom implementations.

Python

n = 1000000  n_str = str(n)  # Converting the number to a string res = ""  # Initializing an empty string to store the formatted result count = 0  # Initializing a counter to track the number of digits processed  # Iterating through the digits of the number in reverse order for digit in reversed(n_str):     res = digit + res  # Adding the current digit to the result string     count += 1       # Adding a comma after every 3 digits, except at the end of the number     if count % 3 == 0 and count != len(n_str):         res = "," + res  # Inserting a comma before the current result  print(res)

Output

1,000,000

Explanation:

This method involves manually looping through the digits of the number and inserting commas after every third digit.
While functional, it requires more code and is less efficient compared to using built-in methods like format() or f-strings.

Using re.sub()

re.sub() function from Python’s regular expressions module can also be used to insert commas into a number string. This method allows more control over how the commas are inserted but is more complex than the built-in methods.

Python

import re   n = 1000000   # The regular expression adds a comma after every group of three digits, starting from the right res = re.sub(r"(?<=\d)(?=(\d{3})+(?!\d))", ",", str(n)) print(res)

Output

1,000,000

Explanation:

re.sub() function uses a regular expression to match positions in the string where commas need to be inserted.
This method is powerful for complex formatting tasks but is not as efficient or readable as format() or f-strings.

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Add Comma Between Numbers - Python

Using format()

Explanation:

Using f-strings

Explanation:

Using locale module

Explanation:

Using str.replace() with a loop

Explanation:

Using re.sub()

Explanation:

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