You opened the file in binary mode: with open(fname, 'rb') as f: This means that all data read from the file is returned as bytes objects, not str. You cannot then use a string in a containment test: if 'some-pattern' in tmp: continue You'd have to use a bytes object to test against tmp instead: if b'some-pattern' in tmp: continue or open the file as a textfile instead by replacing the `'rb'` mode with `'r'.`

You opened the file in binary mode:
with open(fname, 'rb') as f:
This means that all data read from the file is returned as `bytes` objects, not `str`. You cannot then use a string in a containment test:
if 'some-pattern' in tmp: continue
You'd have to use a `bytes` object to test against `tmp` instead:
if b'some-pattern' in tmp: continue
or open the file as a textfile instead by replacing the `'rb'` mode with `'r'`.