How to Pad a Number with Leading Zeros in Python

Q: How do I add leading zeros to a number in Python?

Use an f-string like `f"{n:05d}"` or `str(n).zfill(5)`. Both return a string such as `'00042'`.

Q: Why can't I store an integer with leading zeros?

Integers store only a value, and the value of `007` is just 7. Leading zeros are a display choice, so format the number into a string when you show it.

Q: How do I remove leading zeros from a number string?

Use `int(text)` to get the number, or `text.lstrip("0")` to keep a string. Note `lstrip` turns `"000"` into an empty string.

By Yogesh Sharma (LinkedIn) · Every code example is run and checked on Python 3.13 (how we test) · Last updated 21 Oct 2026

Short answer

Use an f-string: f"{7:03d}" gives '007'. For text that is already a string, "7".zfill(3) gives the same '007'.

Leading zeros are needed for invoice numbers (INV-00042), file names (image_007.png), times (09:05) and fixed-width codes. The catch is that an integer cannot hold leading zeros: 007 is not valid number syntax and int("007") is just 7. So padding always produces a string, which is exactly what you want for display.

There are three good ways to do it; which one you choose depends on whether you start with a number or a string.

Quick facts
Number to padded string	`f"{n:05d}"`
String to padded string	`s.zfill(5)`
Result type	`str`, never `int`
Width meaning	Minimum total length; longer values are never cut

Pad a number with zeros using an f-string

In an f-string, the format spec 05d means: pad with 0, make it at least 5 characters wide, treat the value as a decimal integer. The width can also come from a variable using nested braces.

Python

order = 42
print(f"INV-{order:05d}")
width = 3
print(f"{7:0{width}d}")

Pad a string with zfill()

str.zfill(width) pads a string on the left with zeros. It understands a leading sign, so the zeros go after a minus or plus sign. It only works on strings, so convert numbers with str() first.

Python

print("42".zfill(5))
print("-42".zfill(5))
print(str(9).zfill(2))

Pad with format() or rjust()

format(7, "03d") and "{:03d}".format(7) produce the same result as the f-string and are useful in older code. str.rjust(width, "0") also works for strings, but unlike zfill() it does not treat a minus sign specially, so "-5".rjust(4, "0") gives '00-5'.

Pad floats and use other fill characters

For floats, combine width and precision: f"{3.14159:08.2f}" gives '00003.14'. To pad with something other than zero, put the fill character before the alignment sign: f"{7:*>4}" gives '***7' (the > means right-align). Related: centering text with center().

Which zero-padding method should you use?

Method	Code	Result for 7, width 3
f-string	`f"{n:03d}"`	`'007'`
format()	`format(n, "03d")`	`'007'`
str.format()	`"{:03d}".format(n)`	`'007'`
zfill()	`str(n).zfill(3)`	`'007'`
rjust()	`str(n).rjust(3, "0")`	`'007'`
Float	`f"{n:06.2f}"`	`'007.00'`

Examples you can run

Press Run, then edit the code and run it again.

Number with an f-string

05d pads to five digits with zeros.

Number with an f-string

for order in [7, 42, 1305]:
    print(f"INV-{order:05d}")

Expected outputINV-00007
INV-00042
INV-01305

String with zfill()

zfill() is perfect when the data is already text, such as an ID read from a file.

String with zfill()

codes = ["5", "73", "2048"]
print([code.zfill(4) for code in codes])

Expected output['0005', '0073', '2048']

Format a clock time

Two-digit hours and minutes use 02d.

Format a clock time

hours, minutes = 9, 5
print(f"{hours:02d}:{minutes:02d}")

Expected output09:05

Edge cases: negatives and values that are already wide

zfill() keeps the sign in front; the width never truncates.

Edge cases: negatives and values that are already wide

print(f"{-42:05d}")
print("-42".zfill(5))
print(f"{123456:03d}")

Expected output-0042
-0042
123456

Common mistakes

Trying to write a number with leading zeros

✗ Wrong

invoice = 007

SyntaxError: leading zeros in decimal integer literals are not permitted; use an 0o prefix for octal integers

✓ Right

invoice = 7
print(f"{invoice:03d}")

Store the number as an int and pad it only when you display it.

Calling zfill() on an int

✗ Wrong

print(7.zfill(3))

SyntaxError: invalid decimal literal

✓ Right

print(str(7).zfill(3))

zfill() is a string method. Convert with str() first.

Using d with a string value

✗ Wrong

print(f"{'7':03d}")

ValueError: Unknown format code 'd' for object of type 'str'

✓ Right

print(f"{int('7'):03d}")

Convert to int first, or use zfill() on the string.

How to Pad a Number with Leading Zeros in Python: questions people ask

How do I add leading zeros to a number in Python?

Use an f-string like f"{n:05d}" or str(n).zfill(5). Both return a string such as '00042'.

Why can't I store an integer with leading zeros?

Integers store only a value, and the value of 007 is just 7. Leading zeros are a display choice, so format the number into a string when you show it.

How do I remove leading zeros from a number string?

Use int(text) to get the number, or text.lstrip("0") to keep a string. Note lstrip turns "000" into an empty string.

Keep learning

Step-by-step lessons:
Python f-Strings Python Strings Python Numbers

More in working with text:
How to Reverse a String in Python How to Check if a String Contains a Substring in Python How to Remove Whitespace from a String in Python How to Split a String into Words in Python How to Compare Strings Ignoring Case in Python How to Capitalize the First Letter of a String in Python See all →