Display number with leading zeros

Question

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 output I\'m expe

Answer 1

You can do this with f strings.

import numpy as np

print(f'{np.random.choice([1, 124, 13566]):0>8}')

This will print constant length of 8, and pad the rest with leading 0.

00000001
00000124
00013566

Answer 2

In Python 2.6+ and 3.0+, you would use the format() string method:

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'))

See the PEP-3101 documentation for the new formatting functions.

Answer 3

In Python >= 3.6, you can do this succinctly with the new f-strings that were introduced by using:

f'{val:02}'

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

For your specific example you can do this nicely in a loop:

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

which prints:

01 
10
100

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For more information on f-strings, take a look at PEP 498 where they were introduced.

Answer 4

If dealing with numbers that are either one or two digits:

'0'+str(number)[-2:] or '0{0}'.format(number)[-2:]