Python 操作 PostgreSQL 數據庫
我使用的是 Python 3.7.0
PostgreSQL可以使用psycopg2模塊與Python集成。
sycopg2是用於Python編程語言的PostgreSQL數據庫適配器。
psycopg2是非常小，快速，穩定的。 您不需要單獨安裝此模塊，因為默認情況下它會隨着Python 2.5.x版本一起發布。
pip3 install python-psycopg2
pip3 install psycopg2-binary
連接到數據庫
以下Python代碼顯示了如何連接到現有的數據庫。 如果數據庫不存在，那么它將自動創建，最后將返回一個數據庫對象。
#!/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作為數據庫名稱，如果數據庫已成功打開連接，則會提供以下消息：
Open database successfully
創建表
以下Python程序將用於在先前創建的數據庫(testdb)中創建一個表：
#!/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()
當執行上述程序時，它將在數據庫testdb中創建COMPANY表，並顯示以下消息：
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建的COMPANY表中創建記錄：
#!/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()
當執行上述程序時，它將在COMPANY表中創建/插入給定的記錄，並顯示以下兩行：
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()
執行上述程序時，會產生以下結果：
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語句來更新任何記錄，然后從COMPANY表中獲取並顯示更新的記錄：
#!/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()
執行上述程序時，會產生以下結果：
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 語句來刪除記錄，然后從 COMPANY 表中獲取並顯示剩余的記錄：
#!/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()
執行上述程序時，會產生以下結果：
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
https://www.yiibai.com/postgresql/postgresql_python.html