EP 3 Connaître les différences entre octets, str et unicode

• In Python 3, bytes contains sequences of 8 bit values, str contains sequences of Unicode characters. bytes and str instances cannot be used together with operators such as < or +

• In Python 2, str contains sequences of 8-bit values, unicode contains sequences of Unicode characters. str and unicode can be used together with operators if the str only contains 7-bit ASCII charactoers.
• Use helper functions to ensure that the inputs you operate on are the type of charactoer sequence you expect(8-bit vlaues, UTF-8 encoded characters, Unicode characters, etc)
• If you want to read or write binary data to/from a file always open the file using a binary mode(like 'rb' or 'wb')

Effective Python

Helper function to ensure str or bytes

def to_str(bytes_or_str):
    if instance(bytes_or_str, bytes):
        value = bytes_ot_str.decode('utf-8')
    else:
        value = bytes_or_str
    return value
    
    
def to_bytes(bytes_or_str):
    if isinstance(bytes_or_str, bytes):
        value = bytes_or_str).encode('utf-8')
    else:
        value = bytes_or_str
    return value