Why do 'and' & 'or' return operands in Python?

Question

I\'m going through the LPTHW and I came across something I cannot understand. When will it ever be the case that you want your boolean and or or to

Answer 1

Consider the following use case:

element = dict.has_key('foo') and dict['foo']

Will set element to dict['foo'] if it exists, otherwise False. This is useful when writing a function to return a value or False on failure.

A further use case with or

print element or 'Not found!'

Putting these two lines together would print out dict['foo'] if it exists, otherwise it will print 'Not found!' (I use str() otherwise the or fails when element is 0 (or False) because that s considered falsey and since we are only printing it doesn't matter)

This can be simplified to

print dict.has_key('foo') and str(dict['foo']) or 'Not found!'

And is functionally equivalent to:

if dict.has_key('foo'):
    print dict['foo']
else:
    print 'Not found!'