UnboundLocalError：局部变量‘error’在赋值前被引用

Question

我看过其他关于这个错误的问题，但那些情况通常是因为某个地方变量没有被定义，所以在后面调用的时候就出错了。不过在我的程序里，我在尝试方法之前就定义了这些变量，并且在尝试方法中根据某些条件改变了它们，然后在后面的if语句中调用这些变量，但还是出错了。当Python执行到if语句并试图创建变量text时，它说变量error和error1没有定义（在赋值之前就被引用了）。

err = 0
error = 'No Error Set'
error1 = 'No Error1 Set'
try:
    conn = sqlite3.connect(db_dir)
    for row in conn.execute("select max(date) from eod"):
       mxdate = row
    if mxdate == None:
        pass
    else:
        for row in conn.execute('select date, status from eod where date = ?',(mxdate,)):
            _lst_eod = row
    for row in conn.execute("select * from temp"):
        _crnt_eod = row
    conn.close()
except Exception as error:
    error = str(error)
    err = 1
    logged = 0
    try:
        conn.close()
        time = str(right_datetime())[11:19].replace(':','')
        conn = sqlite3.connect(db_dir)
        conn.execute("insert into error_log (date, user, auth, error, _action) values (?,?,?,?,'Failed to select from eod/temp tables.')",(int(str(_date)+time),cred[0],cred[1],error,))
        conn.commit()
        conn.close()
        logged = 1
    except Exception as error1:
        error1 = str(error1)
if err == 1:
    #An error occured here.
    text = '##Error## An error occured while trying to end the day:\n'+error
    if logged == 0:
        text = text+'\n\nA row was written to the error log.'
    else:
        text = text+'\n\nWrite to Error Log failed due to error:\n'+error1
else:
    ....carry on with the rest of the program.

Answer 1

在Python 3中，当你在except SomeException as e:这行代码中给异常指定一个变量时，退出except块后，这个变量会被删除。

>>> e = "something"
>>> try:
...     1/0
... except ZeroDivisionError as e:
...     print(e)
... 
division by zero
>>> e
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'e' is not defined

你的代码也是这样：在except Exception as error:和except Exception as error1:这两个块中，error和error1在退出时都会被删除。