Can you pass functions as arguments?

[bobueland]

I want to calculate f(0) + f(1) + ...+ f(100) over some function f
which I can change. So I would like to create a function taking f as
argument giving back the sum. How do you do that in Python?

[Paul Rubin]

bo*******@yahoo.com writes:

I want to calculate f(0) + f(1) + ...+ f(100) over some function f
which I can change. So I would like to create a function taking f as
argument giving back the sum. How do you do that in Python?

You can just pass f as an argument. The following is not the most
concise or general way, it just shows how you can pass a function.

def square(x):
return x**2

def sum100(f): # f(0)+f(1)+...+f(100)
s = 0
for i in xrange(101):
s += f(i)
return s

print sum100(square) # pass square as an argument

[Xavier Morel]

bo*******@yahoo.com wrote:

I want to calculate f(0) + f(1) + ...+ f(100) over some function f
which I can change. So I would like to create a function taking f as
argument giving back the sum. How do you do that in Python?

Python functions (and classes, and modules) are first-class objects, so
you can use them as regular objects: send them as arguments, generate
and return them from functions, ...

BTW, if your goal is to create that kind of sums of function results, I
think you'd be interested in using both Python's _generators_ and the
built-in function *sum*.

[Bengt Richter]

On 18 Dec 2005 23:18:48 -0800, Paul Rubin <http://ph****@NOSPAM.invalid> wrote:

bo*******@yahoo.com writes:

I want to calculate f(0) + f(1) + ...+ f(100) over some function f
which I can change. So I would like to create a function taking f as
argument giving back the sum. How do you do that in Python?

You can just pass f as an argument. The following is not the most
concise or general way, it just shows how you can pass a function.

def square(x):
return x**2

def sum100(f): # f(0)+f(1)+...+f(100)
s = 0
for i in xrange(101):
s += f(i)
return s

print sum100(square) # pass square as an argument

or

def square(x): return x*x ... from itertools import imap
sum(imap(square, xrange(101))) 338350

which seems to agree with def sum100(f): ... s = 0
... for i in xrange(101):
... s += f(i)
... return s
... sum100(square) 338350

or if the OP actually wants the specific function, def sum100a(f): return sum(imap(f, xrange(101))) ... sum100a(square)

338350

Regards,
Bengt Richter

[Paul Rubin]

bo**@oz.net (Bengt Richter) writes:

or if the OP actually wants the specific function,

>>> def sum100a(f): return sum(imap(f, xrange(101))) ... >>> sum100a(square)

338350

Similarly with generator comprehension, if I have the syntax right:

def sum100c(f): return sum(f(i) for i in xrange(101))