Using namespace functions, nested functions (global, nonlocal), the function name

The name of a function space

1. Built-in space: storage space python interpreter built-in functions
2. Global space: open runtime py file is stored in the relationship with all variables and values ​​py file (inside out function) is executed after the end of the entire py file will disappear.
3. Local space: a function definition, it will record the correspondence between the function name and the function body (nothing, as long as the memory address will only execute in memory temporarily opened a temporary space, storage function of the variables and values correspondence, disappear with the end of the function)

Loading order: inner space> Global Space> local space

Value order: local spaces> Global Space> inner space

1. Scope

   Global scope: the built-in global space + space

   The local scope: local space

Two nested functions

As long encounters a variable name () function is invoked, there is no () function call is not

After the implementation of a function call, the function body open space is automatically destroyed

2.1 Nesting

def func():
    a = 1
    def foo():
        b = 2
        print(b)  # 2
        print(a)  # 1
        def f1():
            print(b) # 2
        return f1()
    return foo()
print(func())

result:

2
1
2
None

Local variables in space on a space nearby and use the global variable space, two local variables tied for space can not be used interchangeably

2.2 function reference each other

def a():
    a = 1
    c()
    print(c)

def c():
    c = 3
    print(a)
def run():
    a()
run()

result:

<function a at 0x0000000002101E18>
<function c at 0x00000000025B98C8>

The output is a function of the definition of a \ c of the memory address space of the built-in parallel variables can not be used interchangeably

2.3 global and nonlocal

1. global only modify the global variable corresponding to

a = 10
def func():
    global a  # 声明修改全局变量的值
    a += 1
    print(a)
func()
print(a)

result:

11
11

Modify global variables inside the function, if it does not exist in the global variable to create a

lst = ["麻花藤", "刘嘉玲", "詹姆斯"]
def func():
    lst.append("马云")   # 对于可变数据类型可以直接进行访问
    print(lst)
func()
print(lst)

result:

[ 'Twist vine', 'Carina', 'James', 'Ma']
[ 'twist vine', 'Carina', 'James', 'Ma']

2. nonlocal modify variable values ​​nearest local space, it does not modify the value of the global variable space

a = 10
def func():
    def f1():
        a = 20
        def foo():
            nonlocal a
            a += 1
            print(a)   # 21
        foo()
        print(a) # 21
    f1()
func()
print(a)   # 10

Output:

21
21
10

Use three function name

1. The memory address of the function name

   print(func)

2. Function name can be assigned to other variables

3. Function name can be passed as a parameter to the function

   Note the point: when the transfer function names if + () is passed in the function's return value

4. Function name can be used as the function's return value is returned

5. Function name can be used as an element stored in a container