Numbers with leading zeros should be displayed.

Published: 11 February 2022

Category: python

Problem

Given:

a = 1
b = 10
c = 100

How do I display a leading zero for all numbers with less than two digits?

This is the result I’m looking for:

01
10
100

You can accomplish the following in Python 2 (and Python 3):

number = 1
print("%02d" % (number,))

In a nutshell, percent is similar to printf or sprintf (see docs).

The same behavior can be done with format: in Python 3.+.

number = 1
print("{:02d}".format(number))

The similar effect may be done with f-strings in Python 3.6+:

number = 1
print(f"{number:02d}")

Answered by Jack M.

You can use str.zfill to fill in the blanks:

print(str(1).zfill(2))
print(str(10).zfill(2))
print(str(100).zfill(2))

prints:

01
10
100

Answered by Datageek

You’d use the format() string function in Python 2.6 and 3.0+:

for i in (1, 10, 100):
    print('{num:02d}'.format(num=i))

or using the built-in (for a single number):

print(format(i, '02d'))

The new formatting functions are documented in -3101.

Answered by Ber

print('{:02}'.format(1))
print('{:02}'.format(10))
print('{:02}'.format(100))

prints:

01
10
100

Answered by Kresimir

Using the new f-strings introduced in Python >= 3.6, you may perform this quickly by using:

f'{val:02}'

which prints the variable with name val with a fill value of 0 and a width of 2.

You can perform this in a loop for your unique example:

a, b, c = 1, 10, 100
for val in [a, b, c]:
    print(f'{val:02}')

which prints:

01 
10
100

Take a look at PEP 498, where f-strings were first introduced, for more information.