168 – Truthy and Falsy

168 – Truthy and Falsy#

All Python objects have a Truthy/Falsy value which dictates how that object will behaving in a Boolean context.

Most objects are Truthy, with a few exceptions. For the built-in types, you usually have a specific value that is Falsy:

# Falsy values:
0        # zero
0.0      # zero, as a float
""       # empty string
[]       # empty list
{}       # empty dictionari
set()    # empty set
tuple()  # empty tuple
None     # None

Note how the Falsy values are “empty” or stand for “nothing”. All other values of the same corresponding types are Truthy:

1, 2, -43              # any non-zero integer
0.1, 3.4, -3.1         # any non-zero float
"hi", "bye", "  "      # any non-empty string
[0], [[]], [1, 2]      # any non-empty list
{"a": "b"}             # any non-empty dictionary
{1, 2}, {False, True}  # any non-empty set
(0,), ([], True)       # any non-empty tuple

In case you are not sure, you can use the built-in bool to check the Truthy/Falsy value of an object:

print(bool(None))  # False

But when used in Boolean contexts, like if statements or in expressions with the keywords not, and, and or, you don’t need the built-in bool because the Truthy/Falsy values of objects are used automatically.