Python String zfill() Method

The zfill() method returns a copy of the string with '0' characters padded to the left. It adds zeros (0) at the beginning of the string until the length of a string equals the specified width parameter. A leading sign ('+'/'-') is handled by inserting the padding after the sign character.

If the value of the width parameter is less than the length of the string, no filling is done.

Syntax:

str.zfill(width)

Parametrs:

1. width: (Required) The length of the returned string with 0's padded to the left of the original string.

Return Value:

1. Returns copy of the original string with 0's padded at the beginning if width is greater than the length of the string.
2. Returns original string without any changes if the width is lesser than the length of the string.

The following example demonstrates the zfill() method.

num = '100'
print(num.zfill(5))

num = '-100' # with - sign
print(num.zfill(5))

num = '$100' # with $ sign
print(num.zfill(5))

00100
-0100
0$100

Above, the zfill() method will add zeros after the + or - sign, but not after any other symbol such as $, #, etc.

The zfill() method will return the original string if the width is lesser than the length of the string, as shown below.

mystr = '10.00'
print(mystr.zfill(5))

10.00

It works with any string, not necessarily a numeric string.

mystr = '10A'
print(mystr.zfill(5))

0010A

If the width parameter is not specified, then it will raise a TypeError.

num = '100'
print(num.zfill())

Traceback (most recent call last):
File "<pyshell#29>", line 1, in <module>
    num.zfill()
TypeError: zfill() takes exactly one argument (0 given)