From 6347e16a49e565705145b2f059db1340a6f21b7a Mon Sep 17 00:00:00 2001
From: "lake.lai" <yaopower@vip.qq.com>
Date: Mon, 25 Apr 2016 15:16:05 +0800
Subject: [PATCH] =?UTF-8?q?python=E4=B8=AD=E7=9A=84=E9=97=AD=E5=8C=85=20fo?=
 =?UTF-8?q?r=20python=203.x?=
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UnboundLocalError: local variable 'count' referenced before assignment.

什么意思?就是说conut这个变量你没有定义就直接引用了,我不知道这是个什么东西,程序就崩溃了.于是,再python3里面,引入了一个关键字:nonlocal,这个关键字是干什么的?就是告诉python程序,我的这个count变量是再外部定义的,你去外面找吧.然后python就去外层函数找,然后就找到了count=0这个定义和赋值,程序就能正常执行了.
---
 closure.py | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/closure.py b/closure.py
index 47dd67c..57fe5dd 100644
--- a/closure.py
+++ b/closure.py
@@ -1,8 +1,9 @@
 def hellocounter (name):
-    count=[0]
+    count=0 #PYTHON 2.x 中，要写count=[0]
     def counter():
-        count[0]+=1
-        print('Hello,',name,',',count[0],' access!')
+        nonlocal count #PYTHON 2.x 中，此行和下一行要换成count[0]+=1
+        count+=1
+        print('Hello,',name,',',count,' access!')#PYTHON 2.x 中请自觉换成str(count[0])
     return counter
 
 hello = hellocounter('ma6174')
@@ -10,6 +11,18 @@ def counter():
 hello()
 hello()
 
+'''
+执行结果
+>>> hello()
+Hello, ma6174 , 1  access!
+>>> hello()
+Hello, ma6174 , 2  access!
+>>> hello()
+Hello, ma6174 , 3  access!
+'''
+##为什么PYTHON 2.x中不直接写count而用list？这是python2的一个bug,如果用count话,会报这样一个错误:
+##UnboundLocalError: local variable 'count' referenced before assignment.
+
 def make_adder(addend):
     def adder(augend):
         return augend + addend