如何处理“finally”块中的异常？

Question

鉴于以下Python代码：

# Use impyla package to access Impala 
from impala.dbapi import connect 
import logging 

def process(): 
    conn = connect(host=host, port=port) # Mocking host and port 
    try: 
     cursor = conn.cursor() 
     # Execute query and fetch result 
    except: 
     loggin.error("Task failed with some exception") 
    finally: 
     cursor.close() # Exception here! 
     conn.close() 

到因帕拉连接被创建。但由于Impala超时，cursor.close()出现异常。

鉴于潜在的例外情况，关闭cursor和conn的正确方法是什么？

Answer 1

你必须嵌套在try块：

def process(): 
    conn = connect(host=host, port=port) # Mocking host and port 
    try: 
     cursor = conn.cursor() 
     try: 
      # Execute query and fetch result 
     finally: 
      # here cursor may fail 
      cursor.close() 
    except: 
     loggin.error("Task failed with some exception") 
    finally: 
     conn.close() 

为了避免这样的尝试，终于块，你可以使用with语句来：

def process(): 
    conn = connect(host=host, port=port) # Mocking host and port 
    try: 
     with conn.cursor() as cursor: 
      # Execute query and fetch result 
      # cursor is automatically closed 
    except: 
     loggin.error("Task failed with some exception") 
    finally: 
     conn.close()