python 操作Cassandra

2020-08-07 本文已影响0人逍遥_yjz
1.安装

2.数据库的操作

安装依赖包：
pip install cassandra-driver
实例：
# coding:utf-8
from cassandra import ConsistencyLevel
# 引入数据
from cassandra.cluster import Cluster
# 引入DCAwareRoundRobinPolicy模块，可用来自定义驱动程序的行为
# from cassandra.policies import DCAwareRoundRobinPolicy
from cassandra.auth import PlainTextAuthProvider
from cassandra.query import SimpleStatement
import pandas as pd


cluster = Cluster(contact_points=['127.0.0.1'],
                  port=9042)
session = cluster.connect()

# 创建keyspace和table
def createKeySpaceAndTable():
    # 创建KeySpace；使用第一个副本放置策略，即简单策略；选择复制因子为3个副本。
    session.execute("CREATE KEYSPACE test WITH replication = {'class':'SimpleStrategy', 'replication_factor' : 1};")

    # 选择keyspace
    session.execute('use test;')
    # 创建table
    session.execute('create table test.user(name text primary key, age int, email varchar);')
    # 删除table
    # session.execute('drop table test.user;')
    # 关闭Session
    session.shutdown()
    # 关闭Cluster
    cluster.shutdown()


'''查询keyspaces/tables/columns状态'''
def selectAllStatus():
    # 查询keyspaces/tables/columns状态
    print(cluster.metadata.keyspaces)
    print('----------')
    print(cluster.metadata.keyspaces['test'].tables)
    print('----------')
    print(cluster.metadata.keyspaces['test'].tables['user'])
    print('----------')
    print(cluster.metadata.keyspaces['test'].tables['user'].columns)
    print('----------')
    print(cluster.metadata.keyspaces['test'].tables['user'].columns['age'])
    print('----------')
    # 关闭连接
    cluster.shutdown()
    # 查看是否关闭连接
    print(cluster.is_shutdown)

'''插入和查询表中的数据'''
def testInsertAndSelectTable():
    # table中插入数据
    session.execute('insert into test.user (name, age, email) values (%s, %s, %s);', ['aaa', 21, '222@21.com'])
    session.execute('insert into test.user (name, age, email) values (%s, %s, %s);', ['bbb', 22, 'bbb@22.com'])
    session.execute('insert into test.user (name, age, email) values (%s, %s, %s);', ['ddd', 20, 'ccc@20.com'])
    # table中查询数据
    rows = session.execute('select * from test.user;')
    for row in rows:
        print(row)
    # 关闭连接
    cluster.shutdown()
    # 查看是否关闭连接
    print(cluster.is_shutdown)


'''连接远程数据库'''
def testContectRemoteDatabase():
    # 配置Cassandra集群的IP，记得改成自己的远程数据库IP哦
    contact_points = ['1.1.1.1', '2.2.2.2', '3.3.3.3']
    # 配置登陆Cassandra集群的账号和密码，记得改成自己知道的账号和密码
    auth_provider = PlainTextAuthProvider(username='XXX', password='XXX')
    # 创建一个Cassandra的cluster
    cluster = Cluster(contact_points=contact_points, auth_provider=auth_provider)
    # 连接并创建一个会话
    session = cluster.connect()
    # 定义一条cql查询语句
    cql_str = 'select * from keyspace.table limit 5;'
    simple_statement = SimpleStatement(cql_str, consistency_level=ConsistencyLevel.ONE)
    # 对语句的执行设置超时时间为None
    execute_result = session.execute(simple_statement, timeout=None)
    # 获取执行结果中的原始数据
    result = execute_result._current_rows
    # 把结果转成DataFrame格式
    result = pd.DataFrame(result)
    # 把查询结果写入csv
    result.to_csv('连接远程数据库.csv', mode='a', header=True)
    # 关闭连接
    cluster.shutdown()

if __name__ == '__main__':
    # 创建keyspace和table
    #createKeySpaceAndTable()

    # 查询keyspaces/tables/columns状态
    #selectAllStatus()

    # 插入和查询表中的数据
    testInsertAndSelectTable()
Cass云数据库基本操作
 Cassandra入门简介
参考链接：
python 操作Cassandra

1.安装

2.数据库的操作

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