Convert integer to fixed length binary string

Ulrich Eckhardt eckhardt at
Thu Jun 11 07:40:48 EDT 2009

casebash wrote:
> I know the bin function converts an int into a binary string.

Binary string sounds ambiguous. Firstly, everything is binary. Secondly,
strings are byte strings or Unicode strings. In any case, I'm not 100% sure
what you mean - giving an example of input and output would help!

> Unfortunately, I need to know the length of the binary string when it
> is being read in and len(bin(x)) depends on x. Is there any way to
> limit it to 4 bytes?

If you need a piece of four bytes which contain a number in a packed format
similar to the one used in memory, using bin(x) is the wrong way. Instead,
take a look at the struct module:

  import struct
  struct.pack('=L', 255)

Alternatively, also the array module might help.


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