How to read binary files in Python? [duplicate]

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: stackoverflow.com/questions/1035340/… — Guillem Cucurull
– Guillem Cucurull, Commented Nov 28, 2013 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
– John Saxton, Commented Nov 28, 2013 at 20:24
by the way, open(..., 'wb') recreates file, so you'll rean nothing — alko
– alko, Commented Nov 28, 2013 at 20:26
More fundamentally ;-), you opened the file for writing (w), not for reading. Change the open mode to 'rb'. — Tim Peters
– Tim Peters, Commented Nov 28, 2013 at 20:26

lennon310 · Accepted Answer · 2013-11-28 20:40:50Z

0

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

answered Nov 28, 2013 at 20:27

lennon310

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4 Comments

Are you checking for EOF or empty string?

@Keikoku read returns '' on eof.

In binary mode, it returns b''

@Keikoku I guess you meand for py3, I'm not used to it