为什么我的python文件出现了这个错误？

Question

我在Python中使用sqlite模块中时，出现了NameError: name 'cursor' is not defined错误，代码如下：

# coding=utf-8
import sqlite3 as s

gnlb=['1','2','3','4']
istr1=''
istr2=''

while True:
    gn=input('功能：')
    if gn in gnlb:
        break
    print('没有这个功能，请重新输入。')

try:
    if gn=='1':
        con=s.connect('hey.db')
        cursor=con.cursor()
        sql='SELECT id_1, id_2 FROM Hello_world'
        cursor.execute(sql)
        result_set=cursor.fetchall()
        for row in result_set:
            print('ID1：{0}，ID2：{1}'.format(row[0],row[1]))
    elif gn=='2':
        istr1=input()
        istr2=input()
        sql='INSERT INTO Hello_world (id_1, id_2) VALUES (?,?)'
        cursor.execute(sql,[id_1,id_2])
        con.commit()
        print('成功')
except sqlite3.Error as e:
    print('数据发生错误：{}'.format(e))
    con.rollback()
finally:
    if cursor:
        cursor.close()
    if con:
        con.close()

报错内容：
Traceback (most recent call last):
File "nb.py", line 27, in
cursor.execute(sql,[id_1,id_2])
NameError: name 'cursor' is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "nb.py", line 30, in
except sqlite3.Error as e:
NameError: name 'sqlite3' is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "nb.py", line 34, in
if cursor:
NameError: name 'cursor' is not defined
求解！

Answer 1

如果gn输入的不是1，cursor这个数据库句柄就不会被定义声明，最后自然无法关闭这个连接。