mysql数据库链接
#File: ezpymysql.py """A lightweight wrapper around PyMySQL. only for python3 """ import time import logging import traceback import pymysql.cursors version = "0.7" version_info = (0, 7, 0, 0) class Connection(object): """A lightweight wrapper around PyMySQL. """ def __init__(self, host, database, user=None, password=None, port=0, max_idle_time=7 * 3600, connect_timeout=10, time_zone="+0:00", charset = "utf8mb4", sql_mode="TRADITIONAL"): self.host = host self.database = database self.max_idle_time = float(max_idle_time) args = dict(use_unicode=True, charset=charset, database=database, init_command=('SET time_zone = "%s"' % time_zone), cursorclass=pymysql.cursors.DictCursor, connect_timeout=connect_timeout, sql_mode=sql_mode) if user is not None: args["user"] = user if password is not None: args["passwd"] = password # We accept a path to a MySQL socket file or a host(:port) string if "/" in host: args["unix_socket"] = host else: self.socket = None pair = host.split(":") if len(pair) == 2: args["host"] = pair[0] args["port"] = int(pair[1]) else: args["host"] = host args["port"] = 3306 if port: args['port'] = port self._db = None self._db_args = args self._last_use_time = time.time() try: self.reconnect() except Exception: logging.error("Cannot connect to MySQL on %s", self.host, exc_info=True) def _ensure_connected(self): # Mysql by default closes client connections that are idle for # 8 hours, but the client library does not report this fact until # you try to perform a query and it fails. Protect against this # case by preemptively closing and reopening the connection # if it has been idle for too long (7 hours by default). if (self._db is None or (time.time() - self._last_use_time > self.max_idle_time)): self.reconnect() self._last_use_time = time.time() def _cursor(self): self._ensure_connected() return self._db.cursor() def __del__(self): self.close() def close(self): """Closes this database connection.""" if getattr(self, "_db", None) is not None: self._db.close() self._db = None def reconnect(self): """Closes the existing database connection and re-opens it.""" self.close() self._db = pymysql.connect(**self._db_args) self._db.autocommit(True) def query(self, query, *parameters, **kwparameters): """Returns a row list for the given query and parameters.""" cursor = self._cursor() try: cursor.execute(query, kwparameters or parameters) result = cursor.fetchall() return result finally: cursor.close() def get(self, query, *parameters, **kwparameters): """Returns the (singular) row returned by the given query. """ cursor = self._cursor() try: cursor.execute(query, kwparameters or parameters) return cursor.fetchone() finally: cursor.close() def execute(self, query, *parameters, **kwparameters): """Executes the given query, returning the lastrowid from the query.""" cursor = self._cursor() try: cursor.execute(query, kwparameters or parameters) return cursor.lastrowid except Exception as e: if e.args[0] == 1062: pass else: traceback.print_exc() raise e finally: cursor.close() insert = execute ## =============== high level method for table =================== def table_has(self, table_name, field, value): if isinstance(value, str): value = value.encode('utf8') sql = 'SELECT %s FROM %s WHERE %s="%s"' % ( field, table_name, field, value) d = self.get(sql) return d def table_insert(self, table_name, item): '''item is a dict : key is mysql table field''' fields = list(item.keys()) values = list(item.values()) fieldstr = ','.join(fields) valstr = ','.join(['%s'] * len(item)) for i in range(len(values)): if isinstance(values[i], str): values[i] = values[i].encode('utf8') sql = 'INSERT INTO %s (%s) VALUES(%s)' % (table_name, fieldstr, valstr) try: last_id = self.execute(sql, *values) return last_id except Exception as e: if e.args[0] == 1062: # just skip duplicated item pass else: traceback.print_exc() print('sql:', sql) print('item:') for i in range(len(fields)): vs = str(values[i]) if len(vs) > 300: print(fields[i], ' : ', len(vs), type(values[i])) else: print(fields[i], ' : ', vs, type(values[i])) raise e def table_update(self, table_name, updates, field_where, value_where): '''updates is a dict of {field_update:value_update}''' upsets = [] values = [] for k, v in updates.items(): s = '%s=%%s' % k upsets.append(s) values.append(v)
upsets = ','.join(upsets) sql = 'UPDATE %s SET %s WHERE %s="%s"' % ( table_name, upsets, field_where, value_where, ) self.execute(sql, *(values))
1.使用
db = Connection( 'localhost', 'db_name', 'user', 'password' ) # 获取一条记录 sql = 'select * from test_table where id=%s' data = db.get(sql, 2) # 获取多天记录 sql = 'select * from test_table where id>%s' data = db.query(sql, 2) # 插入一条数据 sql = 'insert into test_table(title, url) values(%s, %s)' last_id = db.execute(sql, 'test', 'http://a.com/') # 或者 last_id = db.insert(sql, 'test', 'http://a.com/') # 使用更高级的方法插入一条数据 item = { 'title': 'test', 'url': 'http://a.com/', } last_id = db.table_insert('test_table', item)
一般只需要四个参数就可以建立连接了：
- host：数据库地址，本节就是localhost
- database： 数据库名
- user： 数据库用户名
- password：数据库用户的密码
后面还有几个参数可酌情使用：
- max_idle_time： MySQL server默认8小时闲置就会断开客户端的连接；这个参数告诉客户端闲置多长时间要重新连接；
- time_zone: 这里默认时区为0区，你可以设置为自己的时区，比如东8区 +8:00;
- charset：默认为utf8mb4，即支持moji字符的utf8;
** 2. 操作数据库**
数据库操作分为两类：读和写。
读操作： 使用get()获取一个数据，返回的是一个dict，key就是数据库表的字段；使用query()来获取一组数据，返回的是一个list，其中每个item就是一个dict，跟get()返回的字典一样。
写操作： 使用insert()或execute()，看源码就知道，inseret就是execute的别名。
** 3. 高级操作**
以table_开头的方法：
- table_has() 查询某个值是否存在于表中。查询的字段最好建立的在MySQL中建立了索引，不然数据量稍大就会很慢。
- table_insert() 把一个字典类型的数据插入表中。字典的key必须是表的字段。
- table_update() 更新表中的一条记录。其中, field_where最好是建立了索引，不然数据量稍大就会很慢。
