Booleans
Booleans represent one of two values: True
or False
.
Boolean Values
In programming you often need to know if an expression is True
or False
.
You can evaluate any expression in Python, and get one of two answers, True
or False
.
When you compare two values, the expression is evaluated and Python returns the Boolean answer:
// Some code
print(10 > 9)
print(10 == 9)
print(10 < 9)
Example
Print a message based on whether the condition is True
or False
:
// Some code
a = 200
b = 33
if b > a:
print("b is greater than a")
else:
print("b is not greater than a")
Evaluate Values and Variables
The bool()
function allows you to evaluate any value, and give you True
or False
in return,
Example
Evaluate two variables:
// Some code
x = "Hello"
y = 15
print(bool(x))
print(bool(y))
Most Values are True
Almost any value is evaluated to True
if it has some sort of content.
Any string is True
, except empty strings.
Any number is True
, except 0
.
Any list, tuple, set, and dictionary are True
, except empty ones.
Example
The following will return True:
// Some code
bool("abc")
bool(123)
bool(["apple", "cherry", "banana"])
Some Values are False
In fact, there are not many values that evaluate to False
, except empty values, such as ()
, []
, {}
, ""
, the number 0
, and the value None
. And of course the value False
evaluates to False
.
Example
The following will return False:
//Example code
bool(False)
bool(None)
bool(0)
bool("")
bool(())
bool([])
bool({})
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