python中global与nonlocal比较

python引用变量的顺序： 当前作用域局部变量->外层作用域变量->当前模块中的全局变量->python内置变量

一、global

global关键字用来在函数或其他局部作用域中使用全局变量。但是如果不修改全局变量也可以不使用global关键字。

gcount = 0

def global_test():

 print (gcount)

 

def global_counter():

 global gcount

 gcount +=1

 return gcount

 

def global_counter_test():

 print(global_counter())

 print(global_counter())

 print(global_counter())

二、nonlocal

nonlocal关键字用来在函数或其他作用域中使用外层(非全局)变量。

def make_counter():

 count = 0

 def counter():

 nonlocal count

 count += 1

 return count

 return counter

 

def make_counter_test():

 mc = make_counter()

 print(mc())

 print(mc())

 print(mc())

也可以使用generator来实现类似的counter。如下：

def counter_generator():

 count = 0

 while True:

 count += 1

 yield count

 

def counter_generator_test():

 # below is for python 3.x and works well

 citer = counter_generator().__iter__()

 i = 0

 while(i < 3) : 

 print(citer.__next__())

 i+=1

 

def counter_generator_test2(): 

 #below code don't work

 #because next() function still suspends and cannot exit

 #it seems the iterator is generated every time.

 j = 0

 for iter in counter_generator():

 while(j < 3) : 

 print(iter)

 j+=1

到此这篇关于python中global与nonlocal比较就介绍到这了。青春在我的心中是苦涩的又是甘甜的，是精致的又是粗糙的，是清晰的又是朦胧的，是一杯苦茶，最后却品出清雅之香。更多相关python中global与nonlocal比较内容请查看相关栏目，小编编辑不易，再次感谢大家的支持！