Python Booleans |
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Python Booleans
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Booleans represent one of two values: True or False. Boolean ValuesIn 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: Example print(10 > 9)print(10 == 9)print(10 < 9) Try it Yourself »When you run a condition in an if statement, Python returns True or False: ExamplePrint a message based on whether the condition is True or False: a = 200b = 33if b > a: print("b is greater than a") else: print("b is not greater than a") Try it Yourself » Evaluate Values and VariablesThe bool() function allows you to evaluate any value, and give you True or False in return, ExampleEvaluate a string and a number: print(bool("Hello"))print(bool(15)) Try it Yourself » ExampleEvaluate two variables: x = "Hello"y = 15print(bool(x))print(bool(y)) Try it Yourself » Most Values are TrueAlmost 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. ExampleThe following will return True: bool("abc")bool(123)bool(["apple", "cherry", "banana"]) Try it Yourself » Some Values are FalseIn 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. ExampleThe following will return False: bool(False)bool(None)bool(0)bool("")bool(())bool([]) bool({}) Try it Yourself »One more value, or object in this case, evaluates to False, and that is if you have an object that is made from a class with a __len__ function that returns 0 or False: Example class myclass(): def __len__(self): return 0myobj = myclass()print(bool(myobj)) Try it Yourself » Functions can Return a BooleanYou can create functions that returns a Boolean Value: ExamplePrint the answer of a function: def myFunction() : return Trueprint(myFunction()) Try it Yourself »You can execute code based on the Boolean answer of a function: ExamplePrint "YES!" if the function returns True, otherwise print "NO!": def myFunction() : return Trueif myFunction(): print("YES!")else: print("NO!") Try it Yourself »Python also has many built-in functions that return a boolean value, like the isinstance() function, which can be used to determine if an object is of a certain data type: ExampleCheck if an object is an integer or not: x = 200print(isinstance(x, int)) Try it Yourself » ❮ Previous Next ❯ ★ +1 W3schools Pathfinder Track your progress - it's free! Log in Sign Up |
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