如何编写返回另一个函数的函数？

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)
volume_radius_10(5)
=> 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.

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

 import pymonad


@pymonad.curry
def add(a, b):
return a + b


add5 = add(5)
add5(4)
9

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)
volume_radius_1(1)
=> 3.141592653589793

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_radius_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':
def add(*args):
return "Sum is : "+str(sum(args))
return add
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