Python变量作用域LEGB用法解析

# 装饰器的通用写法
def out(func):
  def inner(*args, **kwargs):
    print("we are checking...", args[0])
    return func(*args, **kwargs)

  return inner
@out
def check_2019_nCov(name):
  return f"now, {name} is very healthy..."


tmp = check_2019_nCov('youge')
print(tmp)

# output
we are checking... youge
now, youge is very healthy...

# 最外层的函数作用是, 给装饰器传递参数
def get_param(*args, **kwargs):
  def out(func):
    def inner(*args, **kwargs):
      print("get params", args, kwargs)
      return func(*args, **kwargs)

    return inner

  return out


@get_param("youge")
def check_2019_nCov(name):
  return f"now, {name} is very healthy..."



tmp = check_2019_nCov("youge")
print(tmp)

# output
get params ('youge',) {}
now, youge is very healthy...

for i in range(10):
  print(i)
  
# 这两句话都用到了 i 但其各自的空间是不一样的.
  
[i for i in range(100)]

# var1 是 global
var1 = 666

def foo():
  # var2 是局部
  var2 = 666
  def foo2():
    # 内嵌的局部
    var3 = 666
    
    # print(var2)
    
print(var3) # G->L 是找不到的哦
# 在 foo2 中 寻找 var2 是 L->E 是ok的
# 在 foo 中 寻找 var2 是 E->L 是不行的

total = 0 # 全局

def sum(a, b):
  """重写内置sum"""
  total = a + b 
  print("局部total:", total)
  
sum(1, 1)
print("全局total:", total)

# output
局部total: 2
全局total: 0

name = "youge"

def change_name():
  name = "youyou"
  

# 希望将 "youge" 改为 "youyou"
change_name()
print(name)

# output
youge

name = "youge"

def change_name():
  
  global name
  name = "youyou"

# 希望将 "youge" 改为 "youyou"
change_name()
print(name)

# output
youyou

name = "jack"

def outer():
  name = "youge"

  # 函数内有一个local函数空间
  def inner():
    name = "youyou"
    print("local:", name)

  inner() # 尝试改掉 嵌套层的 name
  print("encolse:", name)


print("global:", name)

outer()

# output
global: jack
local: youyou
encolse: youge

name = "jack"

def outer():
  name = "youge"

  # 函数内有一个local函数空间
  def inner():
    nonlocal name
    name = "youyou"
    print("local:", name)

  inner() # 尝试改掉 嵌套层的 name
  print("encolse:", name)


print("global:", name)

outer()


# output 
global: jack
local: youyou 
encolse: youyou

name = 'youge'
def change_name():
  name = name + "youyou"

change_name()  
print(name)

# output
UnboundLocalError: local variable 'name' referenced before assignment

# 方式1: 定义个单独的函数来处理
name = 'youge'

def change_name(s):
  name = s + "youyou"
  print(name)

# 全局变量来传递给 函数空间, 即"先定义, 后执行")

change_name(name)  

# output
yougeyouyou

# 方式2: 声明为全局即可, 不推荐
name = 'youge'

def change_name():
  global name
  name = name + "youyou"

change_name()
print(name)

# output
yougeyouyou