You're fairly certain, but with Python 3 you can be completely certain. That's the magic of it. Python 2 will allow this to sometimes work, Python 3 will make

You're fairly certain, but with Python 3 you can be completely certain. That's the magic of it. Python 2 will allow this to sometimes work, Python 3 will make sure this never works, because there's a bytes/text mismatch. It's nice to rule out entire classes of bugs like this from sys import argv import json with open(argv[1], 'rb') as f: json.loads(f.read()) Porting is still difficult. But when we ported from Py2 to Py3, we found a couple issues like this (despite dealing with weird encodings all the time).