Expanding tuples into arguments

Question

Is there a way to expand a Python tuple into a function - as actual parameters?

For example, here expand() does the magic:

some_tuple =          


        

Answer 1

Similar to @Dominykas's answer, this is a decorator that converts multiargument-accepting functions into tuple-accepting functions:

apply_tuple = lambda f: lambda args: f(*args)

Example 1:

def add(a, b):
    return a + b

three = apply_tuple(add)((1, 2))

Example 2:

@apply_tuple
def add(a, b):
    return a + b

three = add((1, 2))

Answer 2

Note that you can also expand part of argument list:

myfun(1, *("foo", "bar"))

Answer 3

myfun(*some_tuple) does exactly what you request. The * operator simply unpacks the tuple (or any iterable) and passes them as the positional arguments to the function. Read more about unpacking arguments.

Answer 4

Take a look at the Python tutorial section 4.7.3 and 4.7.4. It talks about passing tuples as arguments.

I would also consider using named parameters (and passing a dictionary) instead of using a tuple and passing a sequence. I find the use of positional arguments to be a bad practice when the positions are not intuitive or there are multiple parameters.

Answer 5

This is the functional programming method. It lifts the tuple expansion feature out of syntax sugar:

apply_tuple = lambda f, t: f(*t)

Redefine apply_tuple via curry to save a lot of partial calls in the long run:

from toolz import curry
apply_tuple = curry(apply_tuple)

Example usage:

from operator import add, eq
from toolz import thread_last

thread_last(
    [(1,2), (3,4)],
    (map, apply_tuple(add)),
    list,
    (eq, [3, 7])
)
# Prints 'True'