[Python-Dev] Re: PEP 616 -- String methods to remove prefixes and suffixes

On Fri, Mar 20, 2020 at 3:28 PM Victor Stinner vstinner@python.org wrote:

...

The builtin ``str`` class will gain two new methods with roughly the following behavior::

def cutprefix(self: str, pre: str, /) -> str:
    if self.startswith(pre):
        return self[len(pre):]
    return self[:]

I tend to be mistrustful of code that tries to guess the best thing to do, when something expected isn't found.

How about:

def cutprefix(self: str, pre: str, raise_on_no_match: bool=False, /) -> str: if self.startswith(pre): return self[len(pre):] if raise_on_no_match: raise ValueError('prefix not found') return self[:]