#!/usr/bin/env python3

from pathlib import Path

def filter(paths, accept='*', reject=''):
    for p in paths:
        if p.match(accept) and not p.match(reject):
            yield p

def filter2(paths, accept='*', reject=''):
    for p in paths:
        try:
            if p.match(reject):
                continue
        except ValueError:
            pass
        if p.match(accept):
            yield p

print('This works because reject is set to a non-trival value:')
for p in filter((Path(p) for p in ['bux', '.pux']), reject='.*'):
    print('    ', str(p))
print()

print('This works with a more complicated version of filter:')
for p in filter2((Path(p) for p in ['bux', '.pux'])):
    print('    ', str(p))
print()

print('This works even though it should not because value of reject is invalid:')
for p in filter2((Path(p) for p in ['bux', '.pux']), reject=None):
    print('    ', str(p))
print()

print('This fails:')
for p in filter((Path(p) for p in ['bux', '.pux'])):
    print('    ', str(p))
print()