Function object

Everything in python objects

Quote

def f1():
    print('from f1')
    
func = f1
print('f1:', f1)
print('func', func)

# 打印结果：
f1: <function f1 at 0x000002110991D268>
func <function f1 at 0x000002110991D268>

As a function parameter

def f1():
    print('from f1')


def f2(f2_f1):
    print('f2_f1:', f2_f1)

f2(f1)
print('f1:', f1)

# 打印结果：
f2_f1: <function f1 at 0x000001E47029D268>
f1: <function f1 at 0x000001E47029D268>

As a function return value

def f1():
    print('from f1')
    
    
def f2(f2_f1):
    return f2_f1

res = f2(f1)
print('res:', res)
print('f1:', f1)

# 打印结果：
res: <function f1 at 0x0000019F13E7D268>
f1: <function f1 at 0x0000019F13E7D268>

Earth element as a container

def f1():
    print('from f1')


lt = [f1, 12, 3, 4, 5]
lt[0]()

Small exercises

def pay():
    print('支付1e成功')

def withdraw():
    print('提现2e成功')

dic = {
    '1': pay,
    '2': withdraw
}

while True:
    msg = '''
    '1': 支付,
    '2': 提现,
    '3': 退出,
    '''
    print(msg)
    choice = input('>>: ').strip()
    if choice == '3':
        break

    elif choice in dic:
        dic[choice]()

Nested functions

Function inside nested functions

def f1():
    print('from f1')

    def f2():
        print('from f2')
    f2()

f1()

Namespace and scope

Namespaces

Built-in namespace

A built-in method of storage space

Built-in data type method; Python interpreter own method (print / len / list / str / dict)

Global name space

In addition to the built-in global and local call

The local name space

Local call within the function definitions

Namespace order of execution (generated)

Built-in namespace: python interpreter starts when there is a
Global name space: time code executable file will have a global
The local name space: time function call will have a local

Search Order

From the current position to find, can not find in that order, not looking backward: Local> Global> Built-in> error

Scope

Global scope

Built-in namespace + global namespace -> global scope

Local scope

Local namespace -> local scope

Global scope and local scope x x no relationship
Local scope x 1 x 2 and the local scope is nothing, even if a local scope and local scope 2 in the same local scope

global keyword

x = 10
def func():
    global x
    x = 20

func()
print(x)   # 打印20

nonlocal keyword

x = 10
def f1():
    x = 2

    def f2():
        nonlocal x   # nonlocal让x成为额顶层函数的局部，不是让它成为全局
        x = 30

    f2()
    print(x)

f1()
# 打印30

important point

All variable data types can break all the rules above

lt = [10]

def f1():
    lt.append(20)

f1()
print(lt)

# 打印结果：
[10,20]

Function object, scope and name space