day 11 Summary

1. vararg

1.1 Name of the parameter *

def f1(*args):  # 调用函数时，有多少个位置实参，我就接收多少个参数
    print(args)
    
f1()  # () # a是空元组
# f1(1)  # (1, )
# f1(1, 2)
f1(1, 2, 3, 3, 4, 5, 5, 6, 7, 7, 7, 7, 7, 7, 7, )

# *args(约定俗称的),用元组接收 多余 的位置实参

The parameter names 1.2 **

def f1(**kwargs):
print(kwargs)## f1(x=1)  # 空字典
# **kwargs,用字典接收多余的关键字实参

1.3 Name of the argument * (understand)

def f1(a, b, c, e, d, f, g):
    print(a, b, c, e, d, f, g)
    
lt = [1, 2, 3, 4, 5, 6, 7]
# f1(lt[0],lt[1],lt[2],lt[3],lt[4],lt[5],lt[6])
f1(*lt)  # *lt把列表中的元素打散成位置实参依次传给位置形参

1.4 the name of the argument ** (understand)

def f1(z, b):
    print(z, b)
    dic = {'z': 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

2. function object

Everything in python objects

2.1 references

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

func()

2.2 container element

lt = [f1, 1, 2, 3]

print('lt[0]', lt[0])
print('f1', f1)

lt[0]()

2.3 as a function argument

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

f2(f1)

print('f1', f1)

2.4 as a function return value

def f2(f2_f1):
    return f2_f1


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

res()

1. Reference (copy)

2. As a container class elements

3. As a function of the argument

4. As the return value of the function

   Contact function object

def register():
    print('register')


def login():
    print('login')


def withdraw():
    print('wightdraw')


def shopping():
    print('shopping')


func_dict = {
    '1': register,
    '2': login,
    '3': withdraw,
    '4': shopping,
}

print('''
1 注册
2 登录
3 提现
4 购物
''')

while True:
    choice = input('请选择你需要的功能(输入q退出)：')
    if choice == 'q':
        break
    func_dict[choice]()

3. nested function

Print multiplication table

for i in range(1, 10):  # i控制的是行
     for j in range(i):  # j控制的是列
         print(f'{j+1}*{i}={(i)*(j+1)}', end=' ')

     print()  # 打印换行

 '''
 i控制行，j控制列
 i = 1  for j in range(1) j = 0 + 1
 i = 2  for j in range(2) j = 0 + 1 j = 1 + 1
 i = 3  for j in range(3) j = 0 + 1 j = 1 +1 j = 2 + 1
 i = 4
 i = 5

Nested functions: a function which has the function

# 定义函数，只检测语法，不会执行代码
 def f1():
     print('from f1')

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



res = f1()

Internal function defined functions, can not be used outside

4. Name of space and scope

4.1 Variable names / function names - "Name -" namespace: special storage name

4.2 built-in namespace: stores the name of the built-in method

1. 3 Data type method comes with built-in; Python interpreter own built-in method (print / len / list / str / dict)

Global name space: In addition to the built-in global and local call

def f1():
     x = 10
     def f2():
         z = 20

 y = 10

 lt = [1, 2, 3]

The local name space: a local call within the function definitions

4.1 namespace execution (generation) order:

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: start with your current location to find, and then looking for can not be found locally in this order, not against the direction - "Global -" Built - "error

len  =10

 def f1():
     # len = 20

     print(len)

 f1()


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

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

 res = f1()

4.2 Scope

Global scope: built-in namespace + global name space - "global scope

def f1():
     y = 2

     print(1, y)


 y = 10
 f1()

 print(2, y)

 print(y)

Local scope

def f1():
     def f2():
         def f3():
             x = 1
             print(x)

         x = 2
         f3()

     f2()


 f1()

The local scope: Local namespace - 'local name space

Local scope x 1 x 2 and the local scope is also no relationship, then the two even with a local scope, and a local scope local scope

global and nonlocal understand, try not to use

global: breaking the rules described above in point 1

x = 10


def f1():
    global x  # 让global以下的局部的x变成全局的x
    x = 20

f1()
print(x)

nonlocal: breaking the rules above Point 2

x = 10

def f1():
    def f2():
        def f3():
            nonlocal x  # nonlocal让x成为顶层函数的局部，不是让他成为全局  # 压根没有应用情景，尽量不要嵌套函数
            x = 1
        x = 2
       f3()
        print(1, x)
    f2()
def f0():
#     x  = 3  # f1的nonlocal无法修改
#     f1()
f1()
print(2, x)

All variable data types can break all the rules above

lt = [10]

def f1():
    lt.append(12)
    lt[0] = 11
   

f1()
print(lt)python

Remember you do not understand / forget

def f1(i, lt=[]):
    lt.append(i)
    print(lt)

for i in range(10):
    f1(i)


def f1(i, lt):
    lt.append(i)
    print(lt)


for i in range(10):
    f1(i, [])

Defined functions: detect only the syntax, the code is not performed

def f1():
    def f2():
        def f3():
            print('f3')
        f3()


f1()

x = 10
print(x)

def f1():
    x = 10
    print(x)

f1()