Python 放入批处理脚本时文件未运行

Question

I have a python script that connect PostgresSQL.

Below is the script.

import psycopg2

conn = psycopg2.connect('connection string')
try:
  curr = conn.cursor()
  sql_strng = "SELECT * FROM tbl"
  ### Further operations###
except(Exception, psycopg2.Error) as error:
      print("error",error)
finally:
    if (conn):
       conn.close()

The above code works well when I run it from Spyder. But when I try to run this from command prompt using a batch script it gives error as shown below. My batch script:

C:\Users\Anaconda3\python.exe \path\to\python\file

The above batch script is throwing error as follows.

if(conn):
NameError: name 'conn' is not defined

Where I am missing out?

Answer 1

You need to make the connection string global. Also put an exception handler for the connection string as below:

try:
    conn = psycopg2.connect(connection string)
except Exception as e:
    print(e)

This will tell you if your connection has gone through or not

Answer 2

If psycopg2.connect throws an exception, the conn =... assignment is never executed, which means that when you arrive at if (conn) , conn is still undefined.