Conditionally set a relational operator in Python

Question

I wish to create a function which filters a data set, and I wish to pass into that function the logic of whether to search <, > or ==.

Is there a preferred method for this in Python, or do I need to create 3 different unique code bases for each using elif for example

if rel_operator == "gt":
    print("GT OPERATION")
elif rel_operator == "lt":
    print("LT OPERATION")
elif rel_operator == "eq":
    print("EQ OPERATION")

Answer 1

You can use python's built-in operator module:

< corresponds to operator.lt

> corresponds to operator.gt 
# I was hasty in writing le in my comment

== corresponds to operator.eq

Following @Nick A comment you can do this:

d = {'gt': operator.gt.__doc__,
'lt':operator.lt.__doc__,
'eq':operator.eq.__doc__}

rel_operator = 'gt'
d.get(rel_operator)

'gt(a, b) -- Same as a>b.'

Answer 2

As already mentioned in the comments and the other answer you can use the operator module which wraps the comparison operators as callables.

In case you want to pass in a string you could simply get the appropriate callable with getattr:

import operator

rel_operator = "gt"  # for example
real_rel_operator = getattr(operator, rel_operator)

and then call the real_rel_operator with the values as arguments. That works because your strings are already what the functions are called. No need to create a dictionary in this case.