Fixed width number formatting python 3

Question

How do I get an integer to fill 0's to a fixed width in python 3.2 using the format attribute? Example:

a = 1
print('{0:3}'.format(a))

gives ' 1' instead of '001' I want. In python 2.x, I know that this can be done using

print "%03d" % number. 

I checked the python 3 string documentation but wasn't able to get this.

http://docs.python.org/release/3.2/library/string.html#format-specification-mini-language

Thanks.

Bering

Answer 1

Prefix the width with a 0:

>>> '{0:03}'.format(1)
'001'

Also, you don't need the place-marker in recent versions of Python (not sure which, but at least 2.7 and 3.1):

>>> '{:03}'.format(1)
'001'

Steppe

How does this approach work for a full column, where i have 1, and 211 for example and i want to have the output 001 and 211. Thanks – Deaver

Answer 2

Better:

number=12
print(f'number is equal to {number:03d}')

Morganatic

Answer 3

There is built-in string method .zfill for filling 0-s:

>>> str(42).zfill(5)
'00042'
>>> str(42).zfill(2)
'42'

Parson

This works well in my application, where I need binary numbers: bin(42)[2:].zfill(7) gives '0101010'. I don't know how'd I'd make the other answers work. – Indent

Answer 4

In python 3, the prefered way is as follows:

• use f-string (formatted string literal)
• specify the width (the number after the colon) with a leading zero to indicate that you want zero rather than blank if the number is not larger enough.

For example:

a = 20
print(f"number is {a :03}")

Note that there is no space after the colon, otherwise the leading zero has no effect.

Burkley