Question

I’m trying to read a file piece by piece:

def buf_read2(filename, buffer_size):

    with open(filename, 'rb') as f:
        buffer = f.read(buffer_size)

        print buffer  # and do other stuff with it

This doesn’t read the last chunk of the file. For example, if a file is 129 bytes and I set buffer_size to 128, the last byte will not be read.

This old school approach works though:

def buf_read1(filename, buffer_size):

    f = open(filename, 'rb')
    while True:
        buffer = f.read(buffer_size)
        if not buffer:
            break

        print buffer  # and do other stuff with it

    f.close()

What am I doing wrong?

Answer 1

with isn’t a loop, so in your first example, read() only gets called once.

You still need to include a loop:

with open(filename, 'rb') as f:
    while True:
        buffer = f.read(buffer_size)
        if not buffer:
            break
        print buffer  # and do other stuff with it