partial

Sometimes you need to create a function from a more universal one. For example, int() has a base parameter which we would like to freeze to have new base2 function:

>>> int("10")
10
>>> int("10", 2)
2
>>> def base2(x):
...     return int(x, 2)
...
>>> base2("10")
2

The functools.partial allows you to do the same more accurate and semantically clear:

base2 = partial(int, base=2)

It can be helpful when you need to pass a function as an argument to another higher order function, but some arguments should be locked:

>>> list(map(partial(int, base=2), ["1", "10", "100"]))
[1, 2, 4]

Without partial you do something like this:

>>> list(map(lambda x: int(x, base=2), ["1", "10", "100"]))
[1, 2, 4]