PostgreSQL可以使用psycopg2模塊與Python集成。sycopg2是用于Python編程語(yǔ)言的PostgreSQL數(shù)據(jù)庫(kù)適配器。 psycopg2是非常小，快速，穩(wěn)定的。您不需要單獨(dú)安裝此模塊，因?yàn)槟J(rèn)情況下它會(huì)隨著Python 2.5.x版本一起發(fā)布。如果還沒(méi)有在您的機(jī)器上安裝它，那么可以使用yum命令安裝它，如下所示：

$yum install python-psycopg2

要使用psycopg2模塊，必須首先創(chuàng)建一個(gè)表示數(shù)據(jù)庫(kù)的Connection對(duì)象，然后可以選擇創(chuàng)建可以幫助您執(zhí)行所有SQL語(yǔ)句的游標(biāo)對(duì)象。

連接到數(shù)據(jù)庫(kù)

以下Python代碼顯示了如何連接到現(xiàn)有的數(shù)據(jù)庫(kù)。如果數(shù)據(jù)庫(kù)不存在，那么它將自動(dòng)創(chuàng)建，最后將返回一個(gè)數(shù)據(jù)庫(kù)對(duì)象。

#!/usr/bin/python

import psycopg2

conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432")

print "Opened database successfully"

在這里指定使用testdb作為數(shù)據(jù)庫(kù)名稱，如果數(shù)據(jù)庫(kù)已成功打開連接，則會(huì)提供以下消息：

Open database successfully

創(chuàng)建表

以下Python程序?qū)⒂糜谠谙惹皠?chuàng)建的數(shù)據(jù)庫(kù)(testdb)中創(chuàng)建一個(gè)表：

#!/usr/bin/python

import psycopg2

conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432")
print "Opened database successfully"

cur = conn.cursor()
cur.execute('''CREATE TABLE COMPANY
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print "Table created successfully"

conn.commit()
conn.close()

當(dāng)執(zhí)行上述程序時(shí)，它將在數(shù)據(jù)庫(kù)testdb中創(chuàng)建COMPANY表，并顯示以下消息：

Opened database successfully
Table created successfully

插入操作

以下Python程序顯示了如何在上述示例中創(chuàng)建的COMPANY表中創(chuàng)建記錄：

#!/usr/bin/python

import psycopg2

conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432")
print "Opened database successfully"

cur = conn.cursor()

cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (1, 'Paul', 32, 'California', 20000.00 )");

cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (2, 'Allen', 25, 'Texas', 15000.00 )");

cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (3, 'Teddy', 23, 'Norway', 20000.00 )");

cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 )");

conn.commit()
print "Records created successfully";
conn.close()

當(dāng)執(zhí)行上述程序時(shí)，它將在COMPANY表中創(chuàng)建/插入給定的記錄，并顯示以下兩行：

Opened database successfully
Records created successfully

SELECT操作

以下Python程序顯示了如何從上述示例中創(chuàng)建的COMPANY表中獲取和顯示記錄：

#!/usr/bin/python

import psycopg2

conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432")
print "Opened database successfully"

cur = conn.cursor()

cur.execute("SELECT id, name, address, salary  from COMPANY")
rows = cur.fetchall()
for row in rows:
   print "ID = ", row[0]
   print "NAME = ", row[1]
   print "ADDRESS = ", row[2]
   print "SALARY = ", row[3], "\n"

print "Operation done successfully";
conn.close()

執(zhí)行上述程序時(shí)，會(huì)產(chǎn)生以下結(jié)果：

Opened database successfully
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  20000.0

ID =  2
NAME =  Allen
ADDRESS =  Texas
SALARY =  15000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully

更新操作

以下Python代碼顯示了如何使用UPDATE語(yǔ)句來(lái)更新任何記錄，然后從COMPANY表中獲取并顯示更新的記錄：

#!/usr/bin/python

import psycopg2

conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432")
print "Opened database successfully"

cur = conn.cursor()

cur.execute("UPDATE COMPANY set SALARY = 25000.00 where ID=1")
conn.commit
print "Total number of rows updated :", cur.rowcount

cur.execute("SELECT id, name, address, salary  from COMPANY")
rows = cur.fetchall()
for row in rows:
   print "ID = ", row[0]
   print "NAME = ", row[1]
   print "ADDRESS = ", row[2]
   print "SALARY = ", row[3], "\n"

print "Operation done successfully";
conn.close()

執(zhí)行上述程序時(shí)，會(huì)產(chǎn)生以下結(jié)果：

Opened database successfully
Total number of rows updated : 1
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  25000.0

ID =  2
NAME =  Allen
ADDRESS =  Texas
SALARY =  15000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully

刪除操作

以下Python代碼顯示了如何使用DELETE語(yǔ)句來(lái)刪除記錄，然后從COMPANY表中獲取并顯示剩余的記錄：

#!/usr/bin/python

import psycopg2

conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432")
print "Opened database successfully"

cur = conn.cursor()

cur.execute("DELETE from COMPANY where ID=2;")
conn.commit
print "Total number of rows deleted :", cur.rowcount

cur.execute("SELECT id, name, address, salary  from COMPANY")
rows = cur.fetchall()
for row in rows:
   print "ID = ", row[0]
   print "NAME = ", row[1]
   print "ADDRESS = ", row[2]
   print "SALARY = ", row[3], "\n"

print "Operation done successfully";
conn.close()

執(zhí)行上述程序時(shí)，會(huì)產(chǎn)生以下結(jié)果：

Opened database successfully
Total number of rows deleted : 1
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  20000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully

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Python連接PostgreSQL數(shù)據(jù)庫(kù)

連接到數(shù)據(jù)庫(kù)

創(chuàng)建表

插入操作

SELECT操作

更新操作

刪除操作