Python : Get size of string in bytes

Question

I have a string that is to be sent over a network. I need to check the total bytes it is represented in.

sys.getsizeof(string_name) returns extra bytes. For example for sys.getsizeof("a") returns 22 , while one character is only represented in 1 byte in python. Is there some other method to find this ?

Answer 1

If you want the number of bytes in a string, this function should do it for you pretty solidly.

def utf8len(s):
    return len(s.encode('utf-8'))

The reason you got weird numbers is because encapsulated in a string is a bunch of other information due to the fact that strings are actual objects in python.

Its interesting because if you look at my solution to encode the string into 'utf-8', there's an 'encode' method on the 's' object (which is a string). Well, it needs to be stored somewhere right? Hence, the higher than normal byte count. Its including that method, along with a few others :).

Answer 2

You can use len(s.encode()) but there's a caveat.

The size in bytes of a string depends on the encoding you choose (by default "utf-8").

For some multi-byte encodings (e.g. utf-16), string.encode will add a Byte Order Mark (BOM) at the start, which is a sequence of special bytes that inform the reader on the byte endianness used. So the length you get is actually len(BOM) + len(encoded_word).

If you don't want to count the BOM bytes, you can use either the little-endian version of the encoding (adding the suffix "-le") or the big-endian version (adding the suffix "be").

>>> len('ciao'.encode('utf-16'))
10
>>> len('ciao'.encode('utf-16-le'))
8