day11 classroom summary function scope

Vararg

Vararg: refers to a function call, the number of parameters passed may not be fixed

* Parameter (parameter name)

* Args (convention), receiving extra argument position, receiving tuple

def f1(*a) # 调用函数时，有多少个参数，我就接收多少个参数
    print(a)
    
f1() # () # a是空元组
f1(1)   # (1,)
f1(1,2)
f1(1,2,3,4,5,6,7,6,6,)
f1(b=1) #报错

def f1(*abc,b):
    print(abc,b)

f1(b=1) # () 1

** Katachisan

** kwargs, receiving extra keyword arguments dictionary

def f1(**kwargs):
    print(kwargs)
    
    
f1() # 空字典
f1(x=1) # {'x':1}

def f1(*args,**kwargs):
    print('args:',args)
    print('kwargs:'kwagrs)
    
    
f1(11,1,12,2,x=1,y=2,z=3) 
# agrgs:(11,1,12,2)
# kwargs:('x':1,'y':2,'z':3)

def f1(a,b,c,*args,**kwargs):
    print('args:',args)
    print('kwargs:'kwagrs)
    
    
f1(11,1,12,2,x=1,y=2,z=3) 
# agrgs:(2,)
# kwargs:('x':1,'y':2,'z':3)

Remember that is receiving extra value

*Arguments

def f1(a,b,c,d,e,f,g):
    print(a,b,c,d,e,f,g)

lt = [1,2,3,4,5,6,7]
#f1(lt[0],t[1],t[2],t[3],t[4],t[5],t[6]) 换成 f1(*lt)
f1(*lt) # *lt把列表中的元素打散成位置实参一次传给位置形参

# 1 2 3 4 5 6 7

**Arguments

def f1(*args,**kwargs):
    print('args',args)
    print('kwargs',kwargs)
    
# def f1(x,y):  报错   

dic = {'a':1,'b':2} # a=1,b=2
f1(**dic)   # **dic把字典打散成关键字实参然后传给函数f1
 # args()
 # kwargs{'a':1,'b':2}

Function object

Everything in python objects

s = 's1'
lt = ['skdjf']

Functions are first-class objects, namely data processing functions can be used as

def func():
    print()
    
    
print(func)

<function func at 0x10af72f28>

First, the four functions function object

1. Quote

x = 'hello nick'
y = x

f = func
print(f)

<function func at 0x10af72f28>

1. As an argument to a function

len(x)

def foo(m)
    m()
    
    
foo(func)

from func

1. There are as function return values

def foo(x):
    return x

res = foo(func)
print(res)
res()

1. It can be used as container type elements

l = [x]

function_list = [func]
function_list[0]()

from func

Exercise function object

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('选择功能：').strip()
    if choice == '3':
        break
    elif choice in dic :
        dic[choice]()
    

Nested functions

Nested function definition

Internal function defined functions can not be used inside a function defined in an external function.

def f1():
    def f2():
        print('from f2')
    f2()
    
f2() # NameError: name 'f2' is not defined
   

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

from f2

Nested function calls

def max2(x,y):
    if x > y:
        return x
    else:
        return y
    
    
def max4(a,b,c,d):
    res1 = max2(a,b)
    res2 = max2(c,d)
    res = max2(res1,res2)
    return res

print(max4(1,2,3,4))

4

Namespace and scope

First, the name space

Namespace (name spaces): create a variable is actually opened up a new space in memory.

The memory space binding relationship between a variable name and variable stored in memory, and this space is called a namespace .

1. Built-in namespace

Built-in namespace: Store Pyhton interpreter that comes with the name, such asint、float、len

Life cycle: when the interpreter started to take effect, fail when the interpreter is closed

1. Global name space

Global name space: In addition to internal and local names, the rest are stored in the global name space.

The following codex、func、l、z

Life cycle: when the file is executed into effect, expire after file execution

x = 1


def func():
    pass


l = [1, 2]

if 3 > 2:
    if 4 > 3:
        z = 3

1. The local name space

The local name space: the name of the function body for storing generated during a function call, such as the following codef2

Life Cycle: take effect during the function call when the file is executed, expire after the function execution

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

f1() 

1. Loading order

   Built-in - "Global -" local

2. Find the order

   Current - "Global -" Built

x = 1
y = 2
len = 100


def func():
    y = 3
    len = 1000
    print(f"y: {y}")
    print(f"len: {len}")
    # print(a)  # NameError: name 'a' is not defined


func()

s: 3
only: 1000

Second, the scope

Domain refers to a region, i.e. the region scope of action.

1. Global scope

Global Scope: Global effective, global survival, and includes built-in namespace global name space.

# 全局作用域
x = 1


def bar():
    print(x)


bar()

1. Local scope

The local scope: partially valid, temporary storage, containing only the local name space.

# 局部作用域
def f1():
    def f2():
        def f3():
            print(x)
        x = 2
        f3()
    f2()


f1()

1. important point

Note that: the scope of the relationship between the function definition stage fixed die, regardless of the function was called.

# 作用域注意点
x = 1


def f1():  # 定义阶段x=1
    print(x)


def f2():
    x = 2
    f1()


f2()

1

1. global keyword

Modify variables in global scope.

x = 1


def f1():
    x = 2

    def f2():
        #         global x  # 修改全局 输出 3
        x = 3
    f2()


f1()
print(x)

1

1. nonlocal keyword

Modify variables local scope.

x = 1


def f1():
    x = 2

    def f2():
        #         nonlocal x 输出 3
        x = 3

    f2()
    print(x)


f1()