Function handle to a built-in operator in Python

Question

Given the following minimal snippet of code:

def cmp(a, b, cmp):
    return cmp(a, b)

a = 1
b = 2
print(cmp(a, b, operator.__eq__))

I'd just like to give a built-in operator like == or > as a function handle into a function. This would be useful for example, if comparisons all need some pre-checks.

The last line gives an error, as it does not know operator.__eq__. How do I correctly name (and import) that == operator on that line?

@Michael because it's not called __eq__ but eq! I'm guessing the __eq__ object is actually the module's equality operator (e.g. to test if operator == my_module). — acdr
– acdr, Commented Apr 13, 2016 at 9:18
both __eq__ and eq are in the operator module. __eq__ is the magic method, eq is one of the "non-magic" methods of this particular module because it's the operator module. @Michael use operator.eq if you can; __eq__ determines what == means as (at)acdr mentioned. Magic methods (double underscores) allow you to re-define the language on a more fundamental level. Eg. class int(int): def __add__(self,a): print("your mom!") would give some funky results when you later cast something to int() and try to do an addtion. E.g. [int(x) + int(x) for x in "1 2 3". split()] — jDo
– jDo, Commented Apr 13, 2016 at 10:26
@jDo I have a different understanding of the doc (eq being only a copy of __eq__ for convenience and in fact operator.__eq__ is operator.eq evaluates to True here). — mkiever
– mkiever, Commented Apr 13, 2016 at 11:40

mkiever · Accepted Answer · 2016-04-13 11:47:39Z

1

Just add import operator and the code is working.

import operator

def cmp(a, b, _cmp):
    return _cmp(a, b)

a = 1
b = 2
print(cmp(a, b, operator.__eq__))

I have renamed the function parameter for clarity.

answered Apr 13, 2016 at 11:47

mkiever

8915 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Function handle to a built-in operator in Python

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related