在Python中赋值之前引用的局部变量 [英] Local variable referenced before assignment in Python

问题描述

Truel=""
count = 0
finle_touch=False #true after it find the first 3 upperletter

# check if there is 1 lower letter after three upper letter
def one_lower(i):
    count=0
    if i == i.lower:
        finle_touch=True
        Truel=i

# check for 3 upper letter
def three_upper(s):
    for i in s:
        if count == 3:
            if finle_touch==True:
                break
            else:
                one_lower(i)
        elif i == i.upper:
            count +=1
            print(count) #for debug
        else:
            count ==0
            finle_touch=False

stuff="dsfsfFSfsssfSFSFFSsfssSSsSSSS......."
three_upper(stuff)
print(Truel)

所以我在'stuff'上有很多字符串，我想找到1个小写字母，然后3个大写字母淹没.

so I got alot of string on 'stuff' and I like to find 1 lowercase letter that sorrund by 3 uppercase letter.

但是当我运行这段代码时，我得到了:

but when i run this code i get:

Traceback (most recent call last):
  File "C:\Python33\mypy\code.py", line 1294, in <module>
    three_upper(stuff)
  File "C:\Python33\mypy\code.py", line 1280, in three_upper
    if count == 3:
UnboundLocalError: local variable 'count' referenced before assignment

我不明白为什么.预先感谢

i don't understand why. thanks in advance

推荐答案

由于此行，count +=1 python认为count是局部变量，使用if count == 3:时不会搜索全局范围.这就是为什么您遇到该错误.

Due to this line count +=1 python thinks that count is a local variable and will not search the global scope when you used if count == 3:. That's why you got that error.

使用global语句来处理该问题:

Use global statement to handle that:

def three_upper(s): #check for 3 upper letter
    global count
    for i in s:

来自文档:

函数中的所有变量分配将值存储在本地 符号表；而变量引用首先在本地 符号表，然后在全局符号表中，然后在表中 内置名称.因此，不能直接分配全局变量 函数中的值(除非在全局语句中命名)， 尽管它们可能会被引用.

All variable assignments in a function store the value in the local symbol table; whereas variable references first look in the local symbol table, then in the global symbol table, and then in the table of built-in names. Thus, global variables cannot be directly assigned a value within a function (unless named in a global statement), although they may be referenced.

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