Many computer systems offer autocomplete: the ability to guess what you’re about to type based on the first few letters you’ve typed. For instance, if you open up IPython and create a string variable, you can do this:

In [7]: s = 'foo'

In [8]: s.s<tab>
s.split s.splitlines s.startswith s.strip s.swapcase

Source: Autocomplete as an interface | benkuhn.net