Truthiness and falsiness

Truthy and falsey

Python allows many shortcuts with Boolean expressions. Most everything in Python has a truth value. As noted earlier, we refer to the truth values of anything other than Booleans with the whimsical terms 鈥渢ruthy鈥� and 鈥渇alsey鈥� (we also use the terms 鈥渢ruthiness鈥� and 鈥渇alsiness鈥�).

When used in Boolean expressions and conditions for loops or branching (if/elif), truthy values are treated (more-or-less) as True, and falsey values are treated (more-or-less) as False.

Truthy things	Falsey things
any non-zero valued int or float,	0, 0.0
5, -17, 3.1415
any non-empty list,	the empty list, []
['foo'], [0], ['a', 'b', 'c']
any non-empty tuple,	the empty tuple, ()
(42.781, -73.901), ('vladimir')
any non-empty string,	the empty string, ""
"bluster", "kimchee"

This allows us to use conditions such as these:

if x % 2:
    # it's odd
    print(f"{x} is odd")

if not s:
   print("The string, s, is empty!")

If you want to know if something is truthy or falsey in Python, you can pass the value or expression to the Boolean constructor, bool().

>>> bool(1)
True
>>> bool(-1)
True
>>> bool(0)
False
>>> bool('xyz')
True
>>> bool('')
False
>>> bool(None)
False

Copyright 漏 2023鈥�2025 Clayton Cafiero

No generative AI was used in producing this material. This was written the old-fashioned way.