Capping a string according to a maximum size given in bytes in Python

Question

Given an encoding, is there a preconceived way to 'cap' a string according to some given maximum size in bytes. Illustration:

>>> some_string = 'abc'
>>> size_limit = 2
>>> encoding = 'utf-8'
>>> capped_string = cap_to_size(some_string, size_limit, encoding)
>>> capped_string
'ab'

That is, the function cap_to_size (so to speak) cuts away the rightmost characters in the string until the resulting string has the given size. If the given string is smaller than the size limit already, nothing happens and the original string is returned.

In the case of multibyte characters, they should be discarded in their entirety, if one of their bytes exceeds the size limit.

What should happen if the cap occurs in the middle of a multibyte character? — Tim Pietzcker
– Tim Pietzcker, Commented Jun 27, 2015 at 12:27
Good question, didn't think of that since I am dealing with an ASCII-compatiable character set at the moment. But generally, multibyte characters should be discarded in their entirety, if one of their bytes exceeds the size limit. I'll update the question. — zepp133
– zepp133, Commented Jun 27, 2015 at 12:33

Tim Pietzcker · Accepted Answer · 2015-06-27 12:38:59Z

1

Off the top of my head (not well tested yet):

def cap_to_size(some_string, size_limit, encoding):
    result = ""
    for char in some_string:
        size_limit -= len(char.encode(encoding))
        if size_limit >= 0:
            result += char
        else:
            return result

answered Jun 27, 2015 at 12:38

Tim Pietzcker

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