Convert to binary and keep leading zeros in Python

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Question :

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:


bin(1) -> 0b1

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

Is there a way of doing this?

Answer #1:

Use the format() function:

>>> format(14, '#010b')

The format() function simply formats the input following the Format Specification mini language. The # makes the format include the 0b prefix, and the 010 size formats the output to fit in 10 characters width, with 0 padding; 2 characters for the 0b prefix, the other 8 for the binary digits.

This is the most compact and direct option.

If you are putting the result in a larger string, use an formatted string literal (3.6+) or use str.format() and put the second argument for the format() function after the colon of the placeholder {:..}:

>>> value = 14
>>> f'The produced output, in binary, is: {value:#010b}'
'The produced output, in binary, is: 0b00001110'
>>> 'The produced output, in binary, is: {:#010b}'.format(value)
'The produced output, in binary, is: 0b00001110'

As it happens, even for just formatting a single value (so without putting the result in a larger string), using a formatted string literal is faster than using format():

>>> import timeit
>>> timeit.timeit("f_(v, '#010b')", "v = 14; f_ = format")  # use a local for performance
>>> timeit.timeit("f'{v:#010b}'", "v = 14")

But I’d use that only if performance in a tight loop matters, as format(...) communicates the intent better.

If you did not want the 0b prefix, simply drop the # and adjust the length of the field:

>>> format(14, '08b')
Answered By: Martijn Pieters

Answer #2:

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

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)
Answered By: bwbrowning

Answer #3:

I am using


will print

Answered By: rekinyz

Answer #4:

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:])


print binary(1)



based on @Martijn Pieters idea

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

Answer #5:

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

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


  • 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
Answered By: ruohola

Answer #6:

Sometimes you just want a simple one liner:

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

Python 3

Answered By: Mark

Answer #7:

You can use something like this

Answered By: Adam

Answer #8:

you can use rjust string method of python
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’

Answered By: Jaydeep Mahajan

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