Function that call n time another function with arguments

Question

why this code is printing once "potato" instead than 5 times ?

def print_word(word):
    print word
    return


def do_n(function , n):
    for i in range(n):
       function
    return

do_n( print_word("potato") , 5 )

Answer 1

Your code is actually not passing print_word("potato") ("the 'call' to the print_word ") to do_n , but instead it's passing None since print_word returns None . Which means that the only time that print_word ran was at do_n( print_word("potato") , 5 ) . What you can do instead is use functools.partial , which returns a function with the args applied to it:

from functools import partial

def print_word(word):
    print(word)
    return # side note: the "return" isn't necessary 


def do_n(function , n):
    for i in range(n):
       function() # call the function
    return

do_n( partial(print_word,"potato") , 5)

functools.partial :

Return a new partial object which when called will behave like func called with the positional arguments args and keyword arguments keywords. If more arguments are supplied to the call, they are appended to args.

Another way is to use a lambda statement or pass the argument separately:

def print_word(word):
    print(word)
    return # side note: the "return" isn't necessary 

def do_n(function , n):
    for i in range(n):
       function() # call the function
    return

do_n(lambda: print_word("potato"), 5) # use the lambda

Or:

def print_word(word):
    print(word)
    return # side note: the "return" isn't necessary 


def do_n(function , n, *args):
    for i in range(n):
       function(*args) # call the function
    return

do_n(print_word, 5, "potato") # pass the argument of print_word as a separate arg

Answer 2

To pass a function with arguments, you can either pass the arguments separately, or you can do a 'partial' application of the function, where you lock a number of variables. Here is such as solution to your problem, where I have 'partially' applied all variables. But, the function is still not called until the function() statement.

from functools import partial

def print_word(word):
    print word
    return

def do_n(function, n):
    for i in range(n):
        function()
    return

print_potato = partial(print_word, potato)

do_n(print_potato, 5)