CODEWITHSUNDEEP
pythondatabaseconnectivity
Satya Devarakonda
Satya Devarakonda

Reputation: 35

what do you use for dsn in a connection string to connect to oracle using python

I am trying to connect to oracle from python using cx_Oracle. MY login and password on known I don't know what use for a dsn.

I am using tkinter to create a CRUD operations to a oracle db. My function is written to read data from the db. My cx_Oracle.connect fails because I am not passing the right parameters.

I used @localhost:1521:xe for the dsn, but it gave a SyntaxError: positional argument follows keyword argument.

Can you please help me key in the right parameters to connect? I am trying to connect to Oracle 10g express edition.

# -*- coding: utf-8 -*-
#Created on Fri Jul 12 15:50:54 2019

#@author: CGDELL23

import tkinter as tk
import cx_Oracle

class Application(tk.Frame):
    def __init__(self,master=None):
        tk.Frame.__init__(self,master)
        self.grid() 
        self.createWidgets()

    def createWidgets(self):

        #Employee Details
        self.eNameLabel = tk.Label(self,text='Employee Name')
        self.eNameValue = tk.Entry(self)
        self.eNameLabel.grid(row=0,column=0) 
        self.eNameValue.grid(row=0,column=1)

        self.eIdLabel = tk.Label(self, text='Employee Id')
        self.eIdValue = tk.Entry(self)
        self.eIdLabel.grid(row=1,column=0) 
        self.eIdValue.grid(row=1,column=1)

        self.eSalaryLabel = tk.Label(self, text='Employee Salary')
        self.eSalaryValue = tk.Entry(self)
        self.eSalaryLabel.grid(row=2,column=0) 
        self.eSalaryValue.grid(row=2,column=1)

        #CRUD Buttons
        self.CreateButton = tk.Button(self,text='Create', command=self.Create)
        self.CreateButton.grid(row=3,column=0)

        self.ReadButton = tk.Button(self,text='Read', command=self.Read)
        self.ReadButton.grid(row=3,column=1)

        self.UpdateButton = tk.Button(self,text='Update', command=self.Update)
        self.UpdateButton.grid(row=3,column=2)

        self.DeleteButton = tk.Button(self,text='Delete', command=self.Delete)
        self.DeleteButton.grid(row=3,column=3) 

        self.ExitButton = tk.Button(self,text='Exit', command=self.Exited)
        self.ExitButton.grid(row=3,column=4)


    #List the CRUD operations functions    
    def Create(self):
        print ('Create Button Pressed')

    #def Read(self):
    #   print ('Read Button Pressed')

    def Update(self):
        print ('Update Button Pressed')

    def Delete(self):
        print ('Delete Button Pressed')

    def Exited(self):
        print ('Exit Button Pressed')
        exit(0)

class odbc:
    dsn_tns=cx_Oracle.makedsn('localhost','8080',service_name='OracleODBC')
    conn=cx_Oracle.connect(user='wm910',password='wm910','@localhost:1521:xe') 

    def Read(self):
        c=conn.cursor()
        c.execute('select * from Employee where empId = 51')
        for row in c:
            print (row[0], '-', row[1])
        conn.close()


c = Application()
c.master.title('Sample Application')
c.mainloop()

Upvotes: 2

Views: 6288

Answers (1)

Mihai Chelaru
Mihai Chelaru

Reputation: 8262

It looks like you've correctly called the makedsn() function but you never used the value returned when calling connect().

According to the cx_Oracle documentation for connect(), the dsn= parameter can be the following:

The dsn (data source name) is the TNS entry (from the Oracle names server or tnsnames.ora file) or is a string like the one returned from makedsn().

Try changing the your call to connect() to the following:

conn = cx_Oracle.connect(user='wm910', password='wm910', dsn=dsn_tns)

EDIT: Or, as suggested by @ChristopherJones in his comment, replace the dsn_tns variable above with "localhost:1521/xe".

Alternatively, you can use a single string as an argument to connect() as described further down:

If only one parameter is passed, a connect string is assumed which is to be of the format user/password@dsn, the same format accepted by Oracle applications such as SQL*Plus.

Elsewhere in the docs, the sample DSN string provided is like so:

connection = cx_Oracle.connect("hr", "welcome", "localhost/orclpdb")

You can remove user= and password= and use only positional arguments like they did, passing in a valid string for the DSN in that form:

connection = cx_Oracle.connect("wm910", "wm910", "localhost/OracleODBC")

Assuming that the hostname/service_name is localhost/OracleODBC.

Upvotes: 1

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