How to Format a Number with Commas in Python

To format a number with commas in Python, put a comma in the format spec: f"{n:,}" turns 1234567 into 1,234,567. Add a precision for floats, like f"{n:,.2f}":

n = 1234567.5
print(f"{n:,}")     # 1,234,567.5
print(f"{n:,.2f}")  # 1,234,567.50

Everything below ran on Python 3.12.5 and pandas 3.0.6, with US numbers like state populations and dollar revenue.

We’ll cover f-strings, format(), other separators, locale-aware output, pandas columns and turning formatted text back into numbers.

Format a number with commas using an f-string

The , option groups digits in threes. It works on ints and floats, keeps the minus sign, and leaves numbers under 1,000 alone:

population = 39431263          # California, 2024 estimate
revenue = 1284567.5

print(f"{population:,}")       # int with commas
print(f"{revenue:,.2f}")       # float: commas + 2 decimals
print(f"${revenue:,.2f}")      # USD amount
print(f"{-7500000:,}")         # negatives work too
print(f"{1234:,}", f"{999:,}") # short numbers stay short

Output:

39,431,263
1,284,567.50
$1,284,567.50
-7,500,000
1,234 999

The .2f part is ordinary decimal formatting; formatting decimal places with f-strings explains it in depth.

Add commas with format() and str.format()

The same spec works outside f-strings. That’s handy when the pattern is stored in a variable or you’re on older code. Python also accepts _ as the separator:

sales = 2750000.456

print(format(sales, ",.2f"))           # built-in format()
print("{:,}".format(48213))            # str.format()
print("Total: {:>15,.2f}".format(sales))  # width + commas
print(format(1048576, "_"))            # underscore separator
print(format(255000, "_x"))            # "_" groups hex in 4s

Output:

2,750,000.46
48,213
Total:    2,750,000.46
1_048_576
3_e418

If you need literal braces next to the placeholder, see escaping curly braces in Python format strings.

How do I use a period or space as the thousands separator?

The format spec only knows , and _. For European style, format the US way first, then swap the symbols in one pass with str.translate():

amount = 1234567.89

us = f"{amount:,.2f}"
eu = us.translate(str.maketrans(",.", ".,"))   # swap the two symbols
space = us.replace(",", " ")

print("US:   ", us)
print("EU:   ", eu)
print("Space:", space)

Output:

US:    1,234,567.89
EU:    1.234.567,89
Space: 1 234 567.89

Don’t chain two replace() calls for the swap, because the second one undoes the first. Building output strings in general is covered in creating a string with variables in Python.

Format numbers with commas for a locale

When users in different countries see your output, let the locale module pick the symbols. The n format type and locale.format_string(..., grouping=True) both follow the active locale:

import locale

n = 1234567.891
for name in ("en_US.UTF-8", "de_DE.UTF-8"):
    locale.setlocale(locale.LC_ALL, name)
    print(f"{name:12} {locale.format_string('%.2f', n, grouping=True):>14}   {round(n):n}")

locale.setlocale(locale.LC_ALL, "")    # back to the system default

Output:

en_US.UTF-8    1,234,567.89   1,234,568
de_DE.UTF-8    1.234.567,89   1.234.568

Locale settings are process-wide, so I set them once at startup rather than inside a loop in real apps. The locale names must exist on the machine.

Add commas to a pandas column

For a DataFrame, map a format string over the column. Keep the original numbers and store the formatted text in a new column, since text can’t be summed:

import pandas as pd

df = pd.DataFrame({"state": ["California", "Texas", "Florida"],
                   "revenue": [1284567.5, 948210.25, 731004.0]})

df["revenue_fmt"] = df["revenue"].map("{:,.2f}".format)   # new text column
print(df)
print(df["revenue"].dtype, "|", df["revenue_fmt"].dtype)

Output:

        state     revenue   revenue_fmt
0  California  1284567.50  1,284,567.50
1       Texas   948210.25    948,210.25
2     Florida   731004.00    731,004.00
float64 | str

To show money with a dollar sign instead, follow formatting numbers as currency in Python.

Convert a string with commas back to a number

Going the other way, strip the commas before calling float() or int(); both raise ValueError on "1,284":

text = "1,284,567.50"
value = float(text.replace(",", ""))
print(value, type(value).__name__)

print(int("39,431,263".replace(",", "")) + 1)

Output:

1284567.5 float
39431264

For more on that conversion, read converting a string to an integer in Python.

Comma formatting options compared

Code	Result for 1234567.891
f"{n:,}"	1,234,567.891
f"{n:,.2f}"	1,234,567.89
f"{n:_.2f}"	1_234_567.89
f"{round(n):n}" (de_DE locale)	1.234.568

You might also like these related guides:

• Print 2 decimal places in Python
• Round numbers to 2 decimal places in Python
• Print an array with commas in Python
• Pad a string with zeros in Python

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