如何使用python在postgresql中执行sql行？

Question

我使用postgresql 8.4 路由河网，下面是我在pgAdmin 中输入的代码，结果很好，

select * from driving_distance
('select gid as id,
 start_id::int4 as source, end_id::int4 as target,
 shape_leng::double precision as cost from network',
 10, 1000000, false, false);

我已经安装了psycopg2，它成功连接了python和postgresql，

#set up python and postgresql connection
import psycopg2

try:
    conn = psycopg2.connect("dbname = 'routing_template' user = 'postgres' host = 'localhost' password = 'xxxxx'")
except:
    print 'I am unable to connect the database'

现在我需要直接在pyscripter的最上面执行我的sql代码，这些代码要怎么改成python代码呢？

我正在使用 Windows 8.1 x64 下的 postgresql 8.4、python 2.7.6。

Answer 1

使用cursor类的execute方法传递参数

import psycopg2

query = """
    select *
    from driving_distance ($$
        select
            gid as id,
            start_id::int4 as source,
            end_id::int4 as target,
            shape_leng::double precision as cost
        from network
        $$, %s, %s, %s, %s
    )
;"""


conn = psycopg2.connect("dbname=cpn")
cur = conn.cursor()
cur.execute(query, (10, 1000000, False, False))
rs = cur.fetchall()
conn.close()
print rs

注意 Python 中的三引号和 SQL 代码中 Dollar-quoted String Constants 的使用