Python Stripe: 'module' object has no attribute 'Charge'

I have installed Stripe on my MacOSX Mavericks Macbook Pro (python 2.7) using

• pip install --index-url https://code.stripe.com --upgrade stripe
• easy_install --index-url https://code.stripe.com --upgrade stripe
• python setup.py install

but I always get the following error message:

$ sudo python stripe.py
Traceback (most recent call last):
  File "stripe.py", line 1, in <module>
    import stripe
  File "/Users/sebastian/Desktop/stripe.py", line 7, in <module>
    resp = stripe.Charge.create(
AttributeError: 'module' object has no attribute 'Charge'

when I try to execute the following script:

import stripe

stripe.api_key = 'my_test_secret_key'

resp = stripe.Charge.create(
    amount=200,
    currency='usd',
    card={
        'number': '4242424242424242',
        'exp_month': 10,
        'exp_year': 2014
    },
    description='customer@gmail.com'
)