Jan Kaliszewski wrote:
Hello.
IMHO it'd be nice...
1. ...to add:
* operator.is_none -- equivalent to (lambda x: x is None)) * operator.is_not_none -- equivalent tolambda x: x is not None))
...making using 'is None'/'is not None' tests with any(), all(), filter(), itertools.takewhile/dropwhile() more convenient and readable (possibly also optimised for speed).
How is import operator any(map(operator.is_none, iterable)) more convenient and readable than: any(x is None for x in iterable) ? I'm asking this as someone who likes map and other functional tools. Now that we have generator expressions and list comprehensions in the language, wrapping trivial expressions in a function is far less common. Likewise, how could a function call that includes 'x is None' be faster than 'x is None' alone? The overhead of calling the function would have to be negative! We can see this with the existing operator.is_ function: [steve@sylar ~]$ python3 -m timeit -r 15 -s "from operator import is_" "is_(42, None)" 1000000 loops, best of 15: 0.224 usec per loop [steve@sylar ~]$ python3 -m timeit -r 15 "42 is None" 1000000 loops, best of 15: 0.117 usec per loop For comparison purposes: [steve@sylar ~]$ python3 -m timeit -r 15 -s "def f(x): x is None" "f(42)" 1000000 loops, best of 15: 0.378 usec per loop and just for completeness: [steve@sylar ~]$ python3 -m timeit -r 15 -s "from operator import is_; from functools import partial; f = partial(is_, None)" "f(42)" 1000000 loops, best of 15: 0.301 usec per loop The possible time saving compared to a pure-Python function is very small, and there's rarely a need to use a function when you can just use an expression.
2. ...to add:
* operator.anti_caller (or e.g. functools.negator?) -- equivalent to:
def anti_caller(func): def call_and_negate(*args, **kwargs): return not func(*args, **kwargs) return call_and_negate
This seems to be a decorator, so I don't believe it belongs in the operator module. Either way, I don't see the point to it. Why would you use this @functools.negator def spam(x): return something instead of just this? def spam(x): return not something What is your use-case for this function? -- Steven