Display number with leading zeros

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.

In Python 2 (and Python 3) you can do:

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

Basically % is like printf or sprintf (see docs).

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For Python 3.+, the same behavior can also be achieved with format:

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

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For Python 3.6+ the same behavior can be achieved with f-strings:

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

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

prints:

01
10
100

You can use str.zfill:

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

prints:

01
10
100