In Python, I’d like to write a function `make_cylinder_volume(r)` which returns another function. That returned function should be callable with a parameter `h`, and return the volume of a cylinder with height `h` and radius `r`.

I know how to return values from functions in Python, but how do I return another function?

Try this, using Python:

``````import math
def make_cylinder_volume_func(r):
def volume(h):
return math.pi * r * r * h
return volume
``````

Use it like this, for example with `radius=10` and `height=5`:

``````volume_radius_10 = make_cylinder_volume_func(10)
=> 1570.7963267948967
``````

Notice that returning a function was a simple matter of defining a new function inside the function, and returning it at the end – being careful to pass the appropriate parameters for each function. FYI, the technique of returning a function from another function is known as currying.

Using lambdas, also known as anonymous functions, you can abstract out the `volume` function inside the `make_cylinder_volume_func` to a single line. In no way different from Óscar López’s answer, the solution using lambda is still in a sense ‘more functional’.

This is how you can write the accepted answer using a lambda expression:

``````import math
def make_cylinder_volume_fun(r):
return lambda h: math.pi * r * r * h
``````

And then call as you’d any other curried function:

``````volume_radius_1 = make_cylinder_volume_fun(1)
=> 3.141592653589793
``````

Just want to point out that you can do this with pymonad

`````` import pymonad

return a + b

9
``````

I know I am too late to the party, but I think you might find this solution interesting.

``````from math import pi
from functools import partial

def cylinder_volume(r, h):
return pi * r * r * h

make_cylinder_with_radius_2 = partial(cylinder_volume, 2)
make_cylinder_with_height_3 = partial(cylinder_volume, h=3)

print(cylinder_volume(2, 3))            # 37.6991118431
print(make_cylinder_with_height_3(2))   # 37.6991118431
``````

Here is documentation about how `partial` works.

Here is one massive example which covers many of single multiple argument cases in one function

``````def maths(var="NA"):
if var.lower() == 'add':
return "Sum is : "+str(sum(args))
elif var.lower() == 'substract':
def substract(a,b):
if a>b:
return "Difference is : "+str(a-b)
else:
return "Difference is : "+str(b-a)
return substract
elif var.lower() == 'multiply':
def multiply(*args):
temp = 1
for x in args:
temp = temp*x
return "multiplication is : "+str(temp)
return multiply
elif var.lower() == 'divide':
def divide(a,b):
return "Division is : "+str(a/b)
return divide
else:
print("Please choose one of given operations: 'add','substract','multiply','divide'")
``````

Here first call the maths function with the required operation and then use the returned function for the actual calculation