Pompeo Massani: The Money Counter

Python PayPal IPN

PayPal is the fastest, but not the best, way to incorporate payments on your web site and reach a worldwide audience. If you are searching for a Plain Old Python Object (POPO) way to integrate with the Python programming language, you are on your own. The Instant Payment Notification (IPN) page only incorporates ASP, .NET, ColdFusion, Java, Perl and PHP samples. A web search will bring up a ton of Python code. Most of this code will be for frameworks such as Django. The rest will not be specifically for connecting Python with IPN: there will be a lot of extra code you do not need. Here is a translation of the PHP sample code into Python.

Code

also available on GitHub.

#!/usr/bin/python

# PHP to Python translation from: https://cms.paypal.com/cms_content/US/en_US/files/developer/IPN_PHP_41.txt

import urllib
import cgi
import cgitb
import socket, ssl, pprint
import pickle
import sys
import json

cgitb.enable(logdir='../logs/')

form = cgi.FieldStorage()

req = 'cmd=_notify-validate'
for k in form.keys():
	v = form[k]
	value = urllib.quote(v.value.decode('string_escape')) # http://stackoverflow.com/questions/13454/python-version-of-phps-stripslashes
	req = req + '&{0}={1}'.format(k, value)

header = 'POST /cgi-bin/webscr HTTP/1.0\r\n'
header += 'Content-Type: application/x-www-form-urlencoded\r\n'
header += 'Content-Length: ' + str(len(req)) + '\r\n\r\n'

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ssl_sock = ssl.wrap_socket(s)
ssl_sock.connect(('www.sandbox.paypal.com', 443)) # Use this for sandbox testing
# ssl_sock.connect(('www.paypal.com', 443)) # Use this for production

ssl_sock.write(header + req)

data = ssl_sock.read()
VERIFIED = False
while len(data) > 0:
	if 'VERIFIED' in data:
		VERIFIED = True
		break
	elif 'INVALID' in data:
		VERIFIED = False
		break

	data = ssl_sock.read()

ssl_sock.close()

if not VERIFIED:
	print "Content-type: text/plain"
	print
	print "Not Verified"
	sys.exit(1)

fields = {	'item_name': None,
		'item_number': None,
		'payment_status': None,
		'mc_gross': None,
		'mc_currency': None,
		'txn_id': None,
		'receiver_email': None,
		'payer_email': None,
		'custom': None,
	}

for k in fields.keys():
	if k in form:
		fields[k] = form[k].value

item_name = fields['item_name']
item_number = fields['item_number']
payment_status = fields['payment_status']
payment_amount = fields['mc_gross']
payment_currency = fields['mc_currency']
txn_id = fields['txn_id']
receiver_email = fields['receiver_email']
payer_email = fields['payer_email']

# check the payment_status is Completed
# check that txn_id has not been previously processed
#  check that receiver_email is your Primary PayPal email
# check that payment_amount/payment_currency are correct
# process payment

print "Content-type: text/plain"
print
print "Verified"

Resources

1. PayPal Developer Network
2. GitHub projects related to PayPal written in Python