異常處理機制: try…..except…..finally…..

try:
    # 需要捕獲異常的程式碼塊， 必須執行， 如果遇到異常， 調轉到excepct語句；
    # 如果異常能被except後面的Error捕獲， 執行except語句的內容, 然後執行finally；
    # 如果異常不能被except後面的Error捕獲， 直接執行finally;；
    f = open('/etc/passwd')
    # 10/0
    # a
    # f.close()
except ZeroDivisionError as e:
    print e
\# 捕獲異常NameError
 

except NameError as e:
    print e
finally:
    # 必須會執行的語句;
    f.close()
    print "正在關閉檔案......"
    print "hello"

實驗：

print  10/0
print '這時測試會不會內打印出來'
--->>這種情況遇到10/0後直接報錯，程式退出，不會執行第二條列印命令
Traceback (most recent call last):
  File "/Python/root/day09.py", line 12, in <module>
    print  10/0
ZeroDivisionError: integer
 
 division or modulo by zero

try機制

try:
    print  10/0
except Exception as e:
    print e
finally:
    print '這時finally語句'

print '這時測試會不會內打印出來'
--->>
integer division or modulo by zero
這時finally語句
這時測試會不會內打印出來

對於前邊的資料庫程式設計可以這樣

import time
import MySQLdb as mysql


db = {
    'user': 'root'
 
,
    'passwd': 'redhat',
    'host': 'localhost',
    'port': 3306,
    'charset': 'utf8',
    'db': 'user',
}


class mMysql(object):
    ##database形式引數
    def __init__(self, **database):
        ##建立資料庫的連線
        self.user = database['user']
        self.__passwd = database['passwd']
        self.host = database['host']
        self.__port = database['port']
        self.charset = database['charset']
        self.db = database['db']
        self.conn = mysql.connect(user=self.user, passwd=self.__passwd,
                                  host=self.host, port=self.__port,
                                  db=self.db, charset=self.charset)
        ##建立遊標，給資料庫傳送sql語句
        self.cur = self.conn.cursor()
        print '[%s]：資料庫正在連結中...' % time.ctime()

    def is_table_exist(self, table_name):
        self.cur.execute('show tables;')
        for name in self.cur.fetchall():
            if name[0] == table_name:
                return True
        else:
            return False

    def select_table(self, table_name, num=1):
        try:
            self.cur.execute('select * from %s' %table_name)
            for i in self.cur.fetchmany(num):
                print i
        except Exception:
            print '%s不存在' % table_name

    def create_table(self, table_name, **attr):
        s = ''
        try:
            for k, v in attr.items():
                s = s + k + ' ' + v + ','
            s = s.rstrip(',')
            sqli = 'create table %s(%s);' %(table_name, s)
            print 'sqli語句:', sqli
            self.cur.execute(sqli)
            print '%s建立成功' %(table_name)
        except Exception:
            print '%s已經存在了' %(table_name)

    def __del__(self):
        self.cur.close()
        self.conn.close()
        print '[%s]:資料庫正在斷開...' %(time.time())



sql = mMysql(**db)
sql.create_table('userinfo2', user='varchar(10)', age='int')
# sql.__del__()
# sql.select_table('python',2)

丟擲異常raise 異常型別

class AgeError(IOError):
    pass

age = raw_input('Age:')
if not 0<int(age)<=200:
    # raise IOError("age: between 0～200")
    # 丟擲自定義異常
    raise AgeError("age: between 0～200")