>>> assert true
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'true' is not defined
>>> assert True
>>> assert False
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError
>>> assert len(tup) = 10
  File "<stdin>", line 1
    assert len(tup) = 10
                    ^
SyntaxError: invalid syntax
>>> assert len(tup) == 9
>>> assert len(tup) == 5
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError
>>> def check(a, b):
...     assert a == b
...     print 'a equals b'
... 
>>> check(5,5)
a equals b
>>> check(4,5)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in check
AssertionError
>>> def more():
...     check(5,5)
...     check(5,6)
...     print 'after assert fails'
... 
>>> more()
a equals b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in more
  File "<stdin>", line 2, in check
AssertionError
>>>