[python] Convert to binary and keep leading zeros in Python

I'm trying to convert an integer to binary using the bin() function in Python. However, it always removes the leading zeros, which I actually need, such that the result is always 8-bit:

Example:

bin(1) -> 0b1

# What I would like:
bin(1) -> 0b00000001

Is there a way of doing this?

You can use something like this

("{:0%db}"%length).format(num)

you can use rjust string method of python syntax: string.rjust(length, fillchar) fillchar is optional

and for your Question you acn write like this

'0b'+ '1'.rjust(8,'0)

so it wil be '0b00000001'

>>> '{:08b}'.format(1)
'00000001'

See: Format Specification Mini-Language

Note for Python 2.6 or older, you cannot omit the positional argument identifier before :, so use

>>> '{0:08b}'.format(1)
'00000001'      

You can use zfill:

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

prints:

01
10
100

I like this solution, as it helps not only when outputting the number, but when you need to assign it to a variable... e.g. - x = str(datetime.date.today().month).zfill(2) will return x as '02' for the month of feb.

When using Python >= 3.6, the cleanest way is to use f-strings with string formatting:

>>> var = 23
>>> f"{var:#010b}"
'0b00010111'

Explanation:

• var the variable to format
• : everything after this is the format specifier
• # use the alternative form (adds the 0b prefix)
• 0 pad with zeros
• 10 pad to a total length off 10 (this includes the 2 chars for 0b)
• b use binary representation for the number

Sometimes you just want a simple one liner:

binary = ''.join(['{0:08b}'.format(ord(x)) for x in input])

Python 3

You can use the string formatting mini language:

def binary(num, pre='0b', length=8, spacer=0):
    return '{0}{{:{1}>{2}}}'.format(pre, spacer, length).format(bin(num)[2:])

Demo:

print binary(1)

Output:

'0b00000001'

EDIT: based on @Martijn Pieters idea

def binary(num, length=8):
    return format(num, '#0{}b'.format(length + 2))

I am using

bin(1)[2:].zfill(8)

will print

'00000001'