How to read binary files in Python?

Question

I am new to binary files and trying to figure out how to read and manipulate them. I have the following code:

bfile = open('square.bmp', 'wb')

b = bytearray(bfile.read(bn))

while len(b) > 0:
    b = bytearray(bfile.read(bn))
    print(b)

bfile.close()

However, running this code is throwing errors and I do not know what I can replace the "bn" with or declare it as to run read the entire file.

Check this other question, it may be useful: http://stackoverflow.com/questions/1035340/reading-binary-file-in-python — Guillem Cucurull, Nov 28 '13 at 20:23
`bn` is an undefined variable. Typically, `read()` takes a size as a parameter, so you might want to start there. — John Saxton, Nov 28 '13 at 20:24
by the way, `open(..., 'wb')` recreates file, so you'll rean nothing — alko, Nov 28 '13 at 20:26
More fundamentally ;-), you opened the file for writing (`w`), not for reading. Change the open mode to `'rb'`. — Tim Peters, Nov 28 '13 at 20:26

lennon310 · Accepted Answer · 2013-11-28T20:40:50.677

0

with open("square.bmp", "rb") as f:
   b = f.read(1)
   while b != b"":
      b = f.read(1)

edited Nov 28 '13 at 20:40

answered Nov 28 '13 at 20:27

lennon310

Are you checking for EOF or empty string? – MxLDevs Nov 28 '13 at 20:29
@Keikoku read returns `''` on eof. – alko Nov 28 '13 at 20:31
In binary mode, it returns `b''` – MxLDevs Nov 28 '13 at 20:33
@Keikoku I guess you meand for py3, I'm not used to it – alko Nov 28 '13 at 20:34

1 Answers1