Reading binary file and looping over each byte

Question

In Python, how do I read in a binary file and loop over each byte of that file?

Answer 1

Python 3, read all of the file at once:

with open("filename", "rb") as binary_file:
    # Read the whole file at once
    data = binary_file.read()
    print(data)

You can iterate whatever you want using data variable.

Answer 2

To sum up all the brilliant points of chrispy, Skurmedel, Ben Hoyt and Peter Hansen, this would be the optimal solution for processing a binary file one byte at a time:

with open("myfile", "rb") as f:
    while True:
        byte = f.read(1)
        if not byte:
            break
        do_stuff_with(ord(byte))

For python versions 2.6 and above, because:

• python buffers internally - no need to read chunks
• DRY principle - do not repeat the read line
• with statement ensures a clean file close
• 'byte' evaluates to false when there are no more bytes (not when a byte is zero)

Or use J. F. Sebastians solution for improved speed

from functools import partial

with open(filename, 'rb') as file:
    for byte in iter(partial(file.read, 1), b''):
        # Do stuff with byte

Or if you want it as a generator function like demonstrated by codeape:

def bytes_from_file(filename):
    with open(filename, "rb") as f:
        while True:
            byte = f.read(1)
            if not byte:
                break
            yield(ord(byte))

# example:
for b in bytes_from_file('filename'):
    do_stuff_with(b)

Answer 3

if you are looking for something speedy, here's a method I've been using that's worked for years:

from array import array

with open( path, 'rb' ) as file:
    data = array( 'B', file.read() ) # buffer the file

# evaluate it's data
for byte in data:
    v = byte # int value
    c = chr(byte)

if you want to iterate chars instead of ints, you can simply use data = file.read(), which should be a bytes() object in py3.