Az alábbi két logikai érték létezik: az igaz (`True`) és a hamis (`False`)
---
## Boolean Values
In programming you often need to know if an expression is `[True](https://www.w3schools.com/python/ref_keyword_true.asp)` or `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`.
You can evaluate any expression in Python, and get one of two answers, `[True](https://www.w3schools.com/python/ref_keyword_true.asp)` or `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`.
When you compare two values, the expression is evaluated and Python returns the Boolean answer:
### Example
print(10 > 9)
print(10 == 9)
print(10 < 9)
When you run a condition in an if statement, Python returns `[True](https://www.w3schools.com/python/ref_keyword_true.asp)` or `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`:
### Example
Print a message based on whether the condition is `[True](https://www.w3schools.com/python/ref_keyword_true.asp)` or `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`:
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()](https://www.w3schools.com/python/ref_func_bool.asp)` function allows you to evaluate any value, and give you `[True](https://www.w3schools.com/python/ref_keyword_true.asp)` or `[False](https://www.w3schools.com/python/ref_keyword_false.asp)` in return,
### Example
Evaluate a string and a number:
print(bool("Hello"))
print(bool(15))
### Example
Evaluate two variables:
x = "Hello"
y = 15
print(bool(x))
print(bool(y))
---
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---
## Most Values are True
Almost any value is evaluated to `[True](https://www.w3schools.com/python/ref_keyword_true.asp)` if it has some sort of content.
Any string is `[True](https://www.w3schools.com/python/ref_keyword_true.asp)`, except empty strings.
Any number is `[True](https://www.w3schools.com/python/ref_keyword_true.asp)`, except `0`.
Any list, tuple, set, and dictionary are `[True](https://www.w3schools.com/python/ref_keyword_true.asp)`, except empty ones.
### Example
The following will return True:
bool("abc")
bool(123)
bool(["apple", "cherry", "banana"])
---
## Some Values are False
In fact, there are not many values that evaluate to `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`, except empty values, such as `()`, `[]`, `{}`, `""`, the number `0`, and the value `None`. And of course the value `[False](https://www.w3schools.com/python/ref_keyword_false.asp)` evaluates to `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`.
### Example
The following will return False:
bool(False)
bool(None)
bool(0)
bool("")
bool(())
bool([])
bool({})
One more value, or object in this case, evaluates to `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`, and that is if you have an object that is made from a class with a `__len__` function that returns `0` or `[False](https://www.w3schools.com/python/ref_keyword_false.asp)`:
### Example
class myclass():
def __len__(self):
return 0
myobj = myclass()
print(bool(myobj))
---
## Functions can Return a Boolean
You can create functions that returns a Boolean Value:
### Example
Print the answer of a function:
def myFunction() :
return True
print(myFunction())
You can execute code based on the Boolean answer of a function:
### Example
Print "YES!" if the function returns True, otherwise print "NO!":
def myFunction() :
return True
if myFunction():
print("YES!")
else:
print("NO!")
Python also has many built-in functions that return a boolean value, like the `[isinstance()](https://www.w3schools.com/python/ref_func_isinstance.asp)` function, which can be used to determine if an object is of a certain data type:
### Example
Check if an object is an integer or not:
x = 200
print(isinstance(x, int))