如何在python中测试数据库连接?

I am accessing a MySQL database from python via MySQLdb library. I am attempting to test the database connection as shown below.

我正在通过MySQLdb库从python访问MySQL数据库。我正在尝试测试数据库连接，如下所示。

db = MySQLdb.connect(self.server, self.user, 
                     self.passwd, self.schema)
cursor = db.cursor()        
try:
    cursor.execute("SELECT VERSION()")
    results = cursor.fetchone()
    ver = results[0]
    if (ver is None):
        return False
    else:
        return True               
except:
    print "ERROR IN CONNECTION"
    return False

Is this the right way one should test the connectivity when writing unit testcases? If there is a better way, please enlighten!

在编写单元测试用例时，是否应该使用这种方法来测试连接性?如果有更好的办法，请启发!

2 个解决方案

#1

I could be wrong (or misinterpreting your question :) ), but I believe the a connection-related exception gets thrown on MySQLdb.connect(). With MySQLdb, the exception to catch is MySQLdb.Error. Therefore, I would suggest moving the db setup inside of the try block and catching the proper exception (MySQLdb.Error). Also, as @JohnMee mentions, fetchone() will return None if there are no results, so this should work:

我可能是错的(或者误解了您的问题:)，但是我相信在MySQLdb.connect()上抛出了一个与连接相关的异常。对于MySQLdb，要捕获的异常是MySQLdb. error。因此，我建议将db设置移动到try块中并捕获适当的异常(MySQLdb.Error)。而且，正如@JohnMee提到的，如果没有结果，fetchone()将不会返回任何结果，所以这应该是可行的:

try:
    db = MySQLdb.connect(self.server, self.user, 
                         self.passwd, self.schema)
    cursor = db.cursor()        
    cursor.execute("SELECT VERSION()")
    results = cursor.fetchone()
    # Check if anything at all is returned
    if results:
        return True
    else:
        return False               
except MySQLdb.Error:
    print "ERROR IN CONNECTION"
return False

If you don't care about the connection and are just looking to test the execution of the query, I guess you could leave the connection setup outside the try but include MySQLdb.Error in your exception, perhaps as follows:

如果您不关心连接，而只想测试查询的执行，我想您可以将连接设置放在try之外，但包含MySQLdb。您的异常错误，可能如下:

db = MySQLdb.connect(self.server, self.user, 
                     self.passwd, self.schema)
cursor = db.cursor() 

try:
    cursor.execute("SELECT VERSION()")
    results = cursor.fetchone()
    # Check if anything at all is returned
    if results:
        return True
    else:
        return False               
except MySQLdb.Error, e:
    print "ERROR %d IN CONNECTION: %s" % (e.args[0], e.args[1])
return False

This would at least give you a more detailed reason of why it failed.

这至少会给你一个更详细的理由说明为什么它失败了。

#2

Yes. Looks good to me.

是的。我看起来很好。

My personal preferences:

我的个人喜好:

actually throw an exception if no connection
如果没有连接，则抛出异常。
you only need to fetchone, the test for None is superfluous (unless you're keen to enforce a minimum version of the database)
您只需要fetchone，对None的测试是多余的(除非您热衷于执行数据库的最小版本)

#1

try:
    db = MySQLdb.connect(self.server, self.user, 
                         self.passwd, self.schema)
    cursor = db.cursor()        
    cursor.execute("SELECT VERSION()")
    results = cursor.fetchone()
    # Check if anything at all is returned
    if results:
        return True
    else:
        return False               
except MySQLdb.Error:
    print "ERROR IN CONNECTION"
return False