我正在使用 MySQLdb
来操作一个 MySQL
数据库,我有下面的例程,将一些数据注入(inject)到一个名为 urls
的表中>:
def insert_urls(dbconn, filenames):
root = "<path>/"
link = "http://<url>/"
for f in filenames:
filename = root + f + ".html"
local_url = link + f + ".html"
print(filename, local_url)
sql = """
INSERT INTO urls(url, filename) VALUES('%s', '%s');
""" % (local_url, filename)
print(sql)
dbconn.execute_query(sql)
urls
表的声明位于此处:
def create_urls_table():
sql = """
CREATE TABLE IF NOT EXISTS urls (
id INT NOT NULL AUTO_INCREMENT,
url BLOB NOT NULL,
filename BLOB NOT NULL,
PRIMARY KEY(id)
) ENGINE=INNODB;
"""
return sql
dbconn
是Dbconn
类的一个对象,定义为:
class Dbconn:
def __init__(self,
host="",
user="",
pwd="",
database=""):
self.host = host
self.user = user
self.pwd = pwd
self.db = database
self.cursor = None
self.conn = None
try:
self.conn = MySQLdb.connect(host=self.host,
user=self.user,
passwd =self.pwd,
db=self.db)
self.cursor = self.conn.cursor()
print "Connection established"
except MySQLdb.Error, e:
print "An error has occurred ", e
def execute_query(self, sql=""):
try:
self.cursor.execute(sql)
except MySQLdb.Error, e:
print "An error has occurred ", e
运行过程 insert_urls
后,我得到以下输出:
INSERT INTO urls(url, filename) VALUES ('http://<url>/amazon.html','<path>/amazon.html');
INSERT INTO urls(url, filename) VALUES('http://<url>/linkedin.html', '<path>/linkedin.html');
INSERT INTO urls(url, filename) VALUES('http://<url>/nytimes.html', '<path>/nytimes.html');
我可以通过命令行将其手动注入(inject) MySQL
。
但是,在执行 SELECT * FROM urls
查询时,我一无所获。手动插入两行后,我得到:
mysql> select * from urls;
+----+------------------------------------------------+------------------------+
| id | url | filename |
+----+------------------------------------------------+------------------------+
| 19 | http://<url>/yelp.html | <path>/yelp.html |
| 29 | http://<url>/amazon.html | <path>/amazon.html |
+----+------------------------------------------------+------------------------+
请注意 id
值正在递增...这可能意味着数据正在插入,但没有持久化?有人可以帮我吗?
最佳答案
您可能正在使用事务数据库,在这种情况下您必须调用
self.conn.commit()
(的确,INNODB 是一个事务型数据库。)
您可以将 commit
合并到 execute_query
中:
def execute_query(self, sql=""):
try:
self.cursor.execute(sql)
except MySQLdb.Error as e:
print "An error has occurred ", e
self.conn.rollback()
else:
self.conn.commit()
但是,在调用 commit
或 rollback
之前,您可能希望执行多个查询。在这种情况下,您可能希望从 execute_query
中删除 commit
并在需要时显式调用 commit
,或者使用上下文管理器调用 当您退出
。with
套件时提交
请注意,MySQLdb
连接是上下文管理器。你可以写
connection = MySQLdb.connect(
host=config.HOST, user=config.USER,
passwd=config.PASS, db=config.MYDB, )
with connection as cursor:
cursor.execute(...)
并且连接将在退出 with-suite
时调用 connection.commit()
,或者 connection.rollback()
如果有一个异常(exception)。
这是在 MySQLdb.connections.py 中控制它的代码:
def __enter__(self): return self.cursor()
def __exit__(self, exc, value, tb):
if exc:
self.rollback()
else:
self.commit()
关于python - 数据被插入到 MySQL 但不是永久的 - Python,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18477124/