利用SSH連線伺服器並從伺服器上的PG資料庫提取資料，儲存為excel檔案。

Python程式碼如下：

## connectted to postgresql DB in the local PC
import psycopg2
import paramiko
from sshtunnel import SSHTunnelForwarder
import xlsxwriter


#獲取金鑰
private_key=paramiko.RSAKey.from_private_key_file('privacy_key_filepath\\id_rsa')

with SSHTunnelForwarder(
        ssh_address_or_host=('192.168.2.9',22), #ssh主機IP+埠,本例區域網
        ssh_pkey=private_key,
        ssh_username='hrm',        
        remote_bind_address=('127.0.0.1',5432)) as server:  #資料庫伺服器地址及埠
#    server.start() #start ssh sever
    conn=psycopg2.connect(database="test_db",
                          user="tester",
                          password="test_user",
                          host="127.0.0.1",
                          port=server.local_bind_port) 
    print('connected to the DB successfully')    
    cur=conn.cursor()
    L=['title','content','url','user_name'] #列標題
    with xlsxwriter.Workbook('.\\train\\positive.xlsx') as wb1:  #事先需建立好train資料夾
        sheet=wb1.add_worksheet() #建立工作表物件
        bold=wb1.add_format({'bold':True}) #定義加粗的格式物件    
        for l in range(len(L)):
            sheet.write(0,l,L[l],bold) #將列標題插入表格 
        
        SQL1 = "SELECT title,content,url,user_name \
        FROM public.raw_data WHERE sentiment=1 AND created_at < '2018-07-06 12:00:00'"
    
        cur.execute(SQL1)
        numrows=int(cur.rowcount)
        rows=cur.fetchall() #返回全部的查詢結果
        for i in range(numrows):
                g=rows[i]
                sheet.write(i+1,0,g[0])
                sheet.write(i+1,1,g[1])
                sheet.write(i+1,2,g[2])
                sheet.write(i+1,3,g[3])
                #sheet.write(i+1,4,g[4])