Python functional Programming--return function

1.1   return function1.1.1   function as return value

>>> def lazy_sum (*args): # variable parameter

... def sum ():

... Ax = 0

... for i in args: # calling parameters of an external function

.... Ax = ax + I

.... return ax

... return sum-- a function returned here

...

>>>

>>>

>>> lazy_sum (1, 3, 5, 7)

<function Lazy_sum.<locals>.sum at0x2b8091d87268>

>>> lazy_sum (1,3, 5, 7) ()

16

>>> F =lazy_sum (1, 3, 5, 7)

>>> F

<function Lazy_sum.<locals>.sum at0x2b8091d87268>

>>> F ()

16

Note: When we call lazy_sum () , each call will return a new function , even if the same parameters are passed in

>>> f1 = lazy_sum (1, 3, 5, 7, 9)

>>> F2 = lazy_sum (1, 3, 5, 7, 9)

>>> F1 = = F2

False

1.1.2   Closed Package

Look at the closure problem.

>>> def count ():

... fs = []

... for i in range (1, 4):

... def f ():

... return I*i

... fs.append (f)

... return FS

...

>>> F1, F2, F3 = count ()-- variable i all refer to 3

>>>

>>> F1

<function COUNT.<LOCALS>.F at0x2b8091d87488>

>>> F1 ()

9

>>> F2 ()

9

>>> F3 ()

9

the back function references the variable i, but it is not executed immediately. when all 3 functions return, they refer to the variable i has become 3, so the final result is 9.

Rewrite code

>>> def count ():

... def f (j):

... return lambda:j*j-- reference J variable,lambda anonymous function without parameter

... fs = []

... for i in range (1, 4):

... fs.append (f (i))

... return FS

>>> F1 ()

1

>>> F2 ()

4

>>> F3 ()

9

This article is from the "90SirDB" blog, be sure to keep this source http://90sirdb.blog.51cto.com/8713279/1820912

Python Functional Programming--return function