.. _equivalent-to-true:

############
Kind-of True
############

See: `truthiness in Python`_ and Python `truth value testing`_.

There are several places where you will find Python applying a test of True
that is more general than simply ``val == True``.

One example is in ``if`` statements:

>>> val = 'a string'  # A not-empty string is True for truth testing
>>> if val:
...     print('Truth testing of "val" returned True')
Truth testing of "val" returned True

Here the ``if val:`` clause applies Python `truth value testing`_ to ``'a
string'``, and returns True. This is because the truth value testing
algorithm returns True from an not-empty string, and False from an empty
string:

>>> another_val = ''
>>> if another_val:
...     print('No need for a message, we will not get here')

You can see the results of truth value testing using ``bool()`` in Python.
For example:

>>> bool(True)
True
>>> bool(False)
False
>>> bool(['some', 'elements'])  # not-empty list tests as True
True
>>> bool([])  # an empty list tests as False
False
>>> bool(10)  # any number other than zero evaluates as True
True
>>> bool(1)
True
>>> bool(0)
False
>>> bool(None)  # None tests as False
False

Examples of situations in which Python uses truth value testing are ``if``
statements; ``while statements`` and :doc:`assert statements <assert>`.