How can I detect if a file is binary (non-text) in Python?

Yet another method based on file(1) behavior:

>>> textchars = bytearray({7,8,9,10,12,13,27} | set(range(0x20, 0x100)) - {0x7f})>>> is_binary_string = lambda bytes: bool(bytes.translate(None, textchars))

Example:

>>> is_binary_string(open('/usr/bin/python', 'rb').read(1024))True>>> is_binary_string(open('/usr/bin/dh_python3', 'rb').read(1024))False

You can also use the mimetypes module:

import mimetypes...mime = mimetypes.guess_type(file)

It's fairly easy to compile a list of binary mime types. For example Apache distributes with a mime.types file that you could parse into a set of lists, binary and text and then check to see if the mime is in your text or binary list.

If you're using python3 with utf-8 it is straight forward, just open the file in text mode and stop processing if you get an UnicodeDecodeError. Python3 will use unicode when handling files in text mode (and bytearray in binary mode) - if your encoding can't decode arbitrary files it's quite likely that you will get UnicodeDecodeError.

Example:

try:    with open(filename, "r") as f:        for l in f:             process_line(l)except UnicodeDecodeError:    pass # Fond non-text data