Python 3

Use urllib.parse.urlencode:

>>> import urllib.parse
>>> f = { 'eventName' : 'myEvent', 'eventDescription' : 'cool event'}
>>> urllib.parse.urlencode(f)
eventName=myEvent&eventDescription=cool+event

Note that this does not do url encoding in the commonly used sense (look at the output). For that use urllib.parse.quote_plus.

Python 2

You need to pass your parameters into urllib.urlencode() as either a mapping (dict), or a sequence of 2-tuples, like:

>>> import urllib
>>> f = { 'eventName' : 'myEvent', 'eventDescription' : 'cool event'}
>>> urllib.urlencode(f)
'eventName=myEvent&eventDescription=cool+event'