gh-73123: Add a keepempty argument to string, bytes and bytearray split methods by MarkCBell · Pull Request #26222 · python/cpython (original) (raw)

This PR adds an optional keepempty argument to string.split (and similarly for bytes.split, bytearray.split and UserString.split). As described in issue bpo-28937:

• If keepempty is true then empty strings are never stripped out of the result array.
• If keepempty is false then empty strings are always stripped out of the result array.
• If keepempty is None (the default) then the current behaviour is followed in which empty strings are stripped out of the result array if and only if the separator string is None.

To do this it uses a new splitting algorithm which has been designed to be compatible with the existing maxsplit argument. This is roughly:

def split(string, sep=None, maxsplit=None, keepempty=None):

    prune = sep is None if keepempty is None else not keepempty
    if sep is None: sep = ' '
    # Ok, the real implementation actually matches on any whitespace,
    # but matching on ' ' is good enough for this toy example.

    results = []
    count = 0
    i = 0
    j = string.find(sep, i)
    while j >= 0:
        if j > i or not prune:
            if maxsplit is not None and count >= maxsplit:
                break
            results.append(string[i:j])
            count += 1
        i = j + len(sep)
        j = string.find(sep, i)

    if i < len(string) or not prune:
        results.append(string[i:])

    return results

A number of tests have been added to check the correct behaviour.

https://bugs.python.org/issue28937

• Issue: str.split(): allow removing empty strings (when sep is not None) #73123