UnboundLocalError: local variable 'c' referenced before assignment

问题代码：

def outer():    c = 0    def inner():        c += 1        print 'inner'        print c    print 'outer'    return inner()outer()

报错：

UnboundLocalError: local variable 'c' referenced before assignment

解决方法：
1.python2.7使用global

c = 0def outer():    def inner():        global c            # python2.7使用global        c += 1        print 'inner'        print c    print 'outer'    return inner()outer()outer()outer()

输出：

outerinner1outerinner2outerinner3

2.python3使用nonlocal

def outer():    c = 0    def inner():        nonlocal c          # python3使用nonlocal        c += 1        print ('inner')        print (c)    print ('outer')    return inner()outer()outer()outer()

参考：https://www.cnblogs.com/thinking-jxj/p/7681415.html

另外，

def outer():    c = 0    def inner():        print 'inner'        print c             # 直接访问不修改值，不报错    print 'outer'    return inner()outer()outer()outer()

输出：

outerinner0outerinner0outerinner0