you can get a list of available methods or data members of an object by hitting the “TAB” key. For example if you forgot how to spell the function to create an horizontal bar plot you can type matplotlib.pyplot.ba and hit TAB to see the possible completions.

You can get help about a function in the notebook by appending a ? after the function name and executing the cell (with shift-ENTER)
import matplotlib.pyplot
matplotlib.pyplot.barh?
You will get a description of the function at the bottom of the screen looking similar to the following.
