Python Booleans
A boolean is a value that is True or False. A comparison makes a boolean.
Two values only
A bool variable holds one of two values.
is_open = True
is_closed = False
print(is_open)
print(type(is_open))Comparisons make booleans
Here == asks if two values are equal. The signs > and < work like in maths.
print(5 == 5)
print(5 > 8)
print(3 < 7)Judging numbers
Python calls a value truthy when bool() gives True. It calls a value falsy when bool() gives False.
print(bool(1))
print(bool(0))
print(bool(-3))Empty means False
An empty string has no characters. An empty list has no items.
print(bool("hi"))
print(bool(""))
print(bool([1, 2]))
print(bool([]))Example
print(bool(10))
print(bool(0))
print(bool("Ada"))
print(bool(""))
print(bool([5]))
print(bool([]))Key points
- Bool: the type that holds True or False
- Truthy: a value that bool() turns into True
- Falsy: a value that bool() turns into False
- Use bool() to ask how Python judges a value
- Empty values are falsy, like an empty string, an empty list, and 0
- A comparison makes a boolean, like 5 == 5
In this example, each line asks bool() to judge one value. The number 10 is truthy, so it prints True. The number 0 is falsy, so it prints False. The text "Ada" has characters, so it prints True. The empty text prints False. The list [5] has an item, so it prints True. The empty list prints False.
Note
In Python, True and False start with a capital letter.
The word true in small letters is not a value.
Try it Yourself
Edit the code, then press Run.
Running is simulated · Python Playground
Exercise
What does bool() give for an empty string?