如何使用python在postgresql中執行sql行？

Question

我使用postgresql 8.4路由河網，以下是我在pgAdmin中輸入的代碼，結果很好，

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);

我已經安裝了psycopg2並且它成功連接了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'

現在我需要在pyscripter的頂部直接執行我的sql代碼，我應該如何將這些代碼更改為python代碼？

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

Answer 1

使用cursor類的execute方法傳遞參數

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

請注意在Python代碼中使用Python中的三引號和引用美元引用的字符串常量