Mutiplication of n functions

Question

I want to write a function in Python that returns the multiplication of n functions (f1(x) * f2(x) * f3(x) * ... * fn(x)).

I was thinking in something like:

def mult_func(*args):
    return lambda x: args(0)(x) * args(1)(x) ...

but I don't know exactly how to loop through the n functions in args.

Thank you.

Answer 1

Its very simple - just use reduce:

from operator import mul    

def mult_func(*args):
    return lambda x: reduce(mul, (n(x) for n in args), 1)

That's just a generator expression looping through the functions, and reducing by multiplication.

Answer 2

args is just a tuple, but it will be difficult to iterate over them the way you need to in a lambda expression (unless you use reduce). Define a nested function instead.

def mult_func(*args):
    def _(x):
        rv = 1
        for func in args:
            rv *= func(x)
        return rv
    return _

Answer 3

def mult_func(x, *args):
    total = 1
    for func in args:
        total *= func(x)
    return total

Very simply returns the product of all args with input of x.

Quick example:

def square(n):
    return n**2

>>> print mult_func(2, square, square) 
16
>>> print mult_func(2, square, square, square)
64