python bitarray to and from file

Question

I'm writing a large bitarray to a file using this code:

import bitarray
bits = bitarray.bitarray(bin='0000011111') #just an example

with open('somefile.bin', 'wb') as fh:
    bits.tofile(fh)

However, when i attempt to read this data back using:

import bitarray
a = bitarray.bitarray()
with open('somefile.bin', 'rb') as fh:
    bits = a.fromfile(fh)
    print bits

it fails with 'bits' being a NoneType. What am i doing wrong?

Kast

Try a bit of debugging. Is it the writing or the reading that is failing? Does the file exist and contain data after writing it? – Drus

Answer 1

I think "a" is what you want. a.fromfile(fh) is a method which fills a with the contents of fh: it doesn't return a bitarray.

>>> import bitarray
>>> bits = bitarray.bitarray('0000011111')
>>> 
>>> print bits
bitarray('0000011111')
>>> 
>>> with open('somefile.bin', 'wb') as fh:
...     bits.tofile(fh)
... 
>>> a = bitarray.bitarray()
>>> with open('somefile.bin', 'rb') as fh:
...     a.fromfile(fh)
... 
>>> print a
bitarray('0000011111000000')

Detraction

Note: seems that the bitarray is converted to bytes first by appending zeros before saving to the file – Waxler

Answer 2

I think the fromfile() method doesn't return anything. The values are stored in your bitarray 'a'.

Dissolute