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functools.partial

partial

Creates a new function with some of the arguments already filled in (partial application).

Syntax

from functools import partial
functools.partial(func, /, *args, **kwargs) -> partial

Arguments are frozen when the partial is created, not when it is called — that is the difference from a lambda, whose late binding makes every closure in a loop see the variable's final value. Positional arguments are glued on from the left, so to skip the first parameter and pre-fill only the second you use a keyword or, since 3.14, the functools.Placeholder sentinel. Unlike a lambda, a partial object exposes func, args and keywords, prints readably while debugging, and can be pickled.

Examples

from functools import partial
def power(base, exp):
    return base ** exp
square = partial(power, exp=2)
print(square(4))  # → 16
cube = partial(power, exp=3)
print(cube(3))  # → 27
add = lambda a, b: a + b
add10 = partial(add, 10)
print(add10(5))  # → 15
print_sep = partial(print, sep=', ')
print_sep(1, 2, 3)  # → 1, 2, 3

# partial с методом
from functools import partial
int2 = partial(int, base=2)
print(int2('1010'))  # → 10

functools.partial

Syntax

Examples

See also