def contains_three(string): return '3' in stringBut, I wanted to define it like so:
contains_three = functools.partial(operator.__contains__, '3')But, partial only freezes the first arguments and you can't mix and match. I've ran into this before and I thought it would be nice to define a partial function that would allow you to freeze arguments in any position. Here's my implementation:
def custom_partial(func, *const_args, **const_kwds): def result(*args,**kwds): args_iter=iter(args) def convert(value): if value is None: return args_iter.next() else: return value to_call = map(convert, const_args) new_kwds = const_kwds.copy() new_kwds.update(kwds) return func(*(to_call + list(args_iter)), **new_kwds) return resultIs there a test? Of course, there is...
from operator import __contains__ import unittest class Test(unittest.TestCase): def testContains(self): has_three = custom_partial(__contains__, None, '3') self.assertTrue(has_three('1234')) self.assertFalse(has_three('124'))By looking at the test and code, the implementation I chose was to have the value of None to denote any argument I don't want to freeze. I could have created a placeholder value for it, but decided since I haven't had a need to freeze an argument with None to just leave it.
Now, I'm not excited about the implementation, but it satisfies my initial requirements. I'm going to continue to work on this to come up with something more elegant, but for now it works.