关于python变量作用域的疑惑 [英] Doubts about python variable scope

问题描述

可能的重复:
Python 范围规则的简短描述

我写了两个简单的函数:

I wrote two simple functions:

# coding: utf-8
def test():
    var = 1 
    def print_var():
        print var 
    print_var()
    print var 

test()
# 1
# 1
def test1():
    var = 2 
    def print_var():
        print var 
        var = 3 
    print_var()
    print var 

test1()
# raise Exception

相比之下，test1() 在 print var 之后赋值，然后引发异常:UnboundLocalError: local variable 'var' referenced before assignment，我想在我调用内部 print var 的那一刻，var 的值为 2，我错了吗?

In comparison, test1() assigns value after print var, then raise an Exception: UnboundLocalError: local variable 'var' referenced before assignment, I think the moment I call inner print var, var has a value of 2, am I wrong?

推荐答案

是的，您在这里不正确.函数定义引入了一个新的作用域.

Yes, you're incorrect here. Function definition introduces a new scope.

# coding: utf-8
def test():
    var = 1 
    def print_var():
        print var    <--- var is not in local scope, the var from outer scope gets used
    print_var()
    print var 

test()
# 1
# 1
def test1():
    var = 2 
    def print_var():
        print var     <---- var is in local scope, but not defined yet, ouch
        var = 3 
    print_var()
    print var 

test1()
# raise Exception

这篇关于关于python变量作用域的疑惑的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！