Passing a comparison operator with a value into a function

Question

I am defining a function where one parameter should be a comparison operator.

I have tried different versions of transforming commands such as float and input

Code I am trying:

def factor_test(factor1, factor2, criteria1, text, criteria2):
    bool_mask1 = rnt2[factor1].str.contains(criteria1,na=False)
    bool_mask2 = rnt2[factor2] criteria2
    # Returns values that are TRUE i.e. an error, not an Boolean dataframe but actual values
    test_name = rnt2[(bool_mask1) & (bool_mask2)]

criteria2 should be > 0.75:

bool_mask2 = rnt2[factor2] > 0.75

Preferred would be one parameter where I can put in both the > and 0.75, the function should be used about 15 times, with !=, == and <.

Very much related but not exact duplicate: [How to pass an 'if' statement to a function?](https://stackoverflow.com/questions/6665082/how-to-pass-an-if-statement-to-a-function) — Georgy, Jul 09 '19 at 15:53

score 1 · Accepted Answer · answered Jul 09 '19 at 12:17

Use the operator module:

def factor_test(factor1, factor2, criteria1, text, criteria2, op):
    bool_mask1 = rnt2[factor1].str.contains(criteria1,na=False)
    bool_mask2 = op(rnt2[factor2], criteria2)
    test_name = rnt2[(bool_mask1) & (bool_mask2)]

Then call with different operators:

import operator

factor_test(factor1, factor2, criteria1, text, criteria2, operator.le)  # <=
factor_test(factor1, factor2, criteria1, text, criteria2, operator.eq)  # ==
# etc

score 1 · Answer 2 · answered Jul 09 '19 at 16:16

If you want to pass both a comparison operator and its value as one argument you have several options:

Using operator functions and functools.partial:

import operator
from functools import partial

# simple example function
def my_function(condition):
    return condition(1)

two_greater_than = partial(operator.gt, 2)
my_function(two_greater_than)
# True

Using dunder methods:

two_greater_than = (2).__gt__
my_function(two_greater_than)
# True

Using lambda (as in jonrsharpe's comment)

two_greater_than = lambda x: 2 > x
my_function(two_greater_than)
# True

Using a function:

def two_greater_than(x):
    return 2 > x

my_function(two_greater_than)
# True

Applying any of these approaches to your function with several arguments should be trivial.

Passing a comparison operator with a value into a function

2 Answers2