Learning new APIs/classes (beginner question)

[Martin Jones]

In a nutshell: My question is: how do experienced coders learn about
external/third-party classes/APIs?

I'm teaching myself Python through a combination of Hetland's
'Beginning
Python', various online tutorials and some past experience coding
ASP/VBScript. To start to learn Python I've set myself the task of
coding a
viewer/editor for Google Contacts and Google Calendar, mainly because
I've
been experiencing some synchronisation anomalies lately. This has so
far
entailed getting into Google's Contacts API.

Although they give some examples, my searches haven't been able to
pull up
anything approaching comprehensive documentation on each class/method.

Can anyone experienced advise on how they would usually go about
learning to
use third party APIs/classes like these?

With thanks,

Martin