app.py

from flask import Flask, url_for, redirect, request 

from config import config, interface

app = Flask(__name__)

@app.route("/")
def index():
    return """
        <a href="%s">
            <img src="https://www.paypalobjects.com/en_US/i/btn/btn_xpressCheckout.gif">
        </a>
        """ % url_for('paypal_redirect')   

@app.route("/paypal/redirect")
def paypal_redirect():
    kw = {
        'amt': '10.00',
        'currencycode': 'USD',
        'returnurl': url_for('paypal_confirm', _external=True),
        'cancelurl': url_for('paypal_cancel', _external=True),
        'paymentaction': 'Sale'
    }

    setexp_response = interface.set_express_checkout(**kw)
    return redirect(interface.generate_express_checkout_redirect_url(setexp_response.token))     

@app.route("/paypal/confirm")
def paypal_confirm():
    getexp_response = interface.get_express_checkout_details(token=request.args.get('token', ''))

    if getexp_response['ACK'] == 'Success':
        return """
            Everything looks good! <br />
            <a href="%s">Click here to complete the payment.</a>
        """ % url_for('paypal_do', token=getexp_response['TOKEN'])
    else:
        return """
            Oh noes! PayPal returned an error code. <br />
            <pre>
                %s
            </pre>
            Click <a href="%s">here</a> to try again.
        """ % (getexp_response['ACK'], url_for('index'))


@app.route("/paypal/do/<string:token>")
def paypal_do(token):
    getexp_response = interface.get_express_checkout_details(token=token)
    kw = {
        'amt': getexp_response['AMT'],
        'paymentaction': 'Sale',
        'payerid': getexp_response['PAYERID'],
        'token': token,
        'currencycode': getexp_response['CURRENCYCODE']
    }
    interface.do_express_checkout_payment(**kw)   

    return redirect(url_for('paypal_status', token=kw['token']))

@app.route("/paypal/status/<string:token>")
def paypal_status(token):
    checkout_response = interface.get_express_checkout_details(token=token)

    if checkout_response['CHECKOUTSTATUS'] == 'PaymentActionCompleted':
        # Here you would update a database record.
        return """
            Awesome! Thank you for your %s %s purchase.
        """ % (checkout_response['AMT'], checkout_response['CURRENCYCODE'])
    else:
        return """
            Oh no! PayPal doesn't acknowledge the transaction. Here's the status:
            <pre>
                %s
            </pre>
        """ % checkout_response['CHECKOUTSTATUS']

@app.route("/paypal/cancel")
def paypal_cancel():
    return redirect(url_for('index'))

if __name__ == '__main__': 
    app.run(host='127.0.0.1', port=8338, debug=True)