python 操做PostgreSQL

pip install psycopg

Python psycopg2 模块APIs

如下是psycopg2的重要的的模块例程能够知足Python程序与PostgreSQL数据库的工做。

 

 

 

S.N.	API & 描述
1	psycopg2.connect(database="testdb", user="postgres", password="cohondob", host="127.0.0.1", port="5432")  这个API打开一个链接到PostgreSQL数据库。若是成功打开数据库时，它返回一个链接对象。 www.yiibai.com
2	connection.cursor() 该程序建立一个光标将用于整个数据库使用Python编程。 yiibai.com
3	cursor.execute(sql [, optional parameters]) 此例程执行SQL语句。可被参数化的SQL语句（即占位符，而不是SQL文字）。 psycopg2的模块支持占位符用％s标志 yiibai.com 例如：cursor.execute("insert into people values (%s, %s)", (who, age))
4	curosr.executemany(sql, seq_of_parameters) 该程序执行SQL命令对全部参数序列或序列中的sql映射。 www.yiibai.com
5	curosr.callproc(procname[, parameters]) 这个程序执行的存储数据库程序给定的名称。该程序预计为每个参数，参数的顺序必须包含一个条目。
6	cursor.rowcount 这个只读属性，它返回数据库中的行的总数已修改，插入或删除最后 execute*().
7	connection.commit() 此方法提交当前事务。若是不调用这个方法，不管作了什么修改，自从上次调用commit()是不可见的，从其余的数据库链接。
8	connection.rollback() 此方法会回滚任何更改数据库自上次调用commit（）方法。
9	connection.close() 此方法关闭数据库链接。请注意，这并不自动调用commit（）。若是你只是关闭数据库链接而不调用commit（）方法首先，那么全部更改将会丢失！ www.yiibai.com
10	cursor.fetchone() 这种方法提取的查询结果集的下一行，返回一个序列，或者无当没有更多的数据是可用的。
11	cursor.fetchmany([size=cursor.arraysize]) 这个例程中取出下一个组的查询结果的行数，返回一个列表。当没有找到记录，返回空列表。该方法试图获取尽量多的行所显示的大小参数。
12	cursor.fetchall() 这个例程获取全部查询结果（剩余）行，返回一个列表。空行时则返回空列表。 www.yiibai.com

链接到数据库

Python代码显示了如何链接到一个现有的数据库。若是数据库不存在，那么它就会被建立，最终将返回一个数据库对象

#!/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" 

建立表

如下Python程序将使用之前建立的数据库中建立一个表：

#!/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()

INSERT 操做

Python程序显示了咱们如何建立表COMPANY 在上面的例子中建立表中的记录：

#!/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()

SELECT 操做

Python程序，显示如何获取并显示COMPANY 表在上面的例子中建立的记录：

#!/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()  

当上述程序执行时，它会产生如下结果

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

UPDATE 操做

Python代码显示如何，咱们能够使用UPDATE语句来更新记录，而后从COMPANY表获取并显示更新的记录

#!/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()  

DELETE 操做

Python代码显示了如何咱们能够使用DELETE语句删除记录，而后获取并显示COMPANY 表剩余的记录： 

#!/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()