在git找了几个blog的源码，在学习的过程中，发现有人使用Connection()，有人却在使用MongoClient()，那么到底两者有什么差别呢？
且看分析如下：
db = Connection('192.168.1.101', 27017).performance_test
#client = MongoClient('192.168.1.101', 27017)
#db = client.performance_test
db.drop_collection("updates")
collection = db.updates
collection.insert({"x": 1})
collection.find_one()
start = time.time()
for i in range(100000):
collection.update({}, {"$push" : {"x" : 1}})
...
运行结果：
>python test_mongo_conn.py
8.43799996376
>python test_mongo_client.py
62.5780000687
用Connection() 8秒，MongoClient()则花了62秒，这性能相差也太多了。
很是疑惑，于是查了pymongo的文档，原来两者有个选项的默认行为不同：
class pymongo.connection.Connection([host='localhost'[, port=27017[, max_pool_size=10[, network_timeout=None[, document_class=dict[, tz_aware=False[, **kwargs]]]]]]])
Write Concern options:
safe: Connection disables acknowledgement of write operations. Use safe=True to enable write acknowledgement.
w: (integer or string) If this is a replica set, write operations will block until they have been replicated to the specified number or tagged set of servers. w=<int> always includes the replica set primary (e.g. w=3 means write to the primary and wait until replicated to two secondaries). Implies safe=True.
wtimeout: (integer) Used in conjunction with w. Specify a value in milliseconds to control how long to wait for write propagation to complete. If replication does not complete in the given timeframe, a timeout exception is raised. Implies safe=True.
j: If True block until write operations have been committed to the journal. Ignored if the server is running without journaling. Implies safe=True.
fsync: If True force the database to fsync all files before returning. When used with j the server awaits the next group commit before returning. Implies safe=True.
safe选项决定操作是“瞬时完成”与“安全操作”，connection()默认是safe=False,即瞬时完成，不等服务器回应，而MongoClient()默认是safe=True，即安全操作，等服务器确认后才继续下一步操作。
所以一个8秒，一个62秒，这个差距实际上是“瞬时完成”与“安全操作”两者的性能差别。
当将Connection() 和MongoClient()建立连接时指定相同的safe参数，两者的性能表现是一样的。
client = MongoClient('192.168.1.101', 27017,safe=False)
#db = Connection('192.168.1.101', 27017,safe=False).performance_test
结论：Python用Connection()连接时，修改操作速度非常快，而用MongoClient()建立的连接，操作速度慢很多。
顺便分享账号密码登录的代码：
from pymongo import MongoClient client = MongoClient('www.yeayee.com','27017') client.database.authenticate("user","password") db = client.database collection = db.collection