request.py

#!/usr/bin/env python3

# This snippet provides the code to make an HTTP request using Python 3's
# built-in libraries, with the following properties:
# - POST request
# - send form-encoded data
# - the URL is behind HTTP basic authentication
#
# The motivating example is making API requests to a service such as Mailgun.
#
# If you can, you should probably use the Requests library
# (http://python-requests.org) instead of the built-in libraries.

ENCODING = 'ascii'
def base64_encode(string):
    """
    Encode the given string with base64, returning the value as a string.
    """
    string_as_bytes = string.encode(ENCODING)
    encoded = base64.b64encode(string_as_bytes)
    return encoded.strip().decode(ENCODING)

def post_request(url, form_fields, username, password):
    """
    Make a POST request to the given URL, authenticating with the provided
    credentials, and sending the given form fields.
    """
    req = urllib.request.Request(url)

    # Accessing the URL requires using HTTP basic authentication. urllib's
    # built-in HTTPBasicAuthHandler doesn't seem to work (at least for me).
    # Therefore, construct the Authorization header manually. The logic is
    # borrowed from the well-known requests library, which does the same thing.
    credentials = '%s:%s' % (username, password)
    auth = base64_encode(credentials)
    header_content = "Basic %s" % auth
    req.add_header('Authorization', header_content)

    # Encode form fields
    data = urllib.parse.urlencode(form_fields)
    data = data.encode('utf-8')

    # Execute request
    f = urllib.request.urlopen(req, data)
    return f.read().decode('utf-8')