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?

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? — Daniel Roseman
– Daniel Roseman, Commented Jun 7, 2011 at 14:09

DSM · Accepted Answer · 2011-06-07 14:12:08Z

12

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')

answered Jun 7, 2011 at 14:12

DSM

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1 Comment

zyxue Over a year ago

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

Reto Aebersold · Accepted Answer · 2011-06-07 14:12:45Z

1

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

answered Jun 7, 2011 at 14:12

Reto Aebersold

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