def foo():
x = ‘hello world’
return x # return ‘hello world’ would do, too

foo()
print x    # NameError - x is not defined outside the function

y = foo()
print y    # this works

x = foo()
print x    # this also works, and it's a completely different x than that inside
           # foo()

z = bar(x) # of course, now you can use x as you want

z = bar(foo()) # but you don't have to