[Python-ideas] Provide a 'key' argument for all() and any() builtins

This would be similar to 'key' argument already available for min(), max() and sorted() and would let user decide what must be considered True and what not. Some use cases: all(a, b, c, ... key=callable) all(a, b, c, ... key=lambda x: isinstance(x, int)) any(a, b, c, ... key=lambda x: x < 10) a = b = c = None for x in foo: if cond1: a = 0 elif cond2: b = 0 elif cond3: c = 0 # meaning all cond* has been satisfied and it's ok to consider 0 a meaningful value assert all(a, b, c, key=lambda x: x != None) Thoughts? --- Giampaolo http://code.google.com/p/pyftpdlib/ http://code.google.com/p/psutil/ http://code.google.com/p/pysendfile/