Boolean

Boolean Values

The Python type for storing true and false values is called bool. There are only two Boolean values: True and False.

True, False are capitalized, no quotes like around strings.

Don't use True/False as variable names.

Boolean Expression

A Boolean expression is an expression that evaluates to a Boolean value. The comparison operators, compare two values and produce True or False according to the relationship of the two values.

There are six common comparison operators:

Work with any data type:

equal to, == Not equal to, !=

Can only work with numbers:

Greater than, > Greater than or equal to, > = Less than or equal to, < = Less than, <

Run the following examples and check the console results:

print(25 == 5*5)    # True
print(25 != 25)     # False
print(25 > 5**2)    # False
print(25 >= 5**2)   # True

print('hi' == 'Hi')        # False (stings are case sensitive)
print('Cat' != 'Chicken')   # True

p = 10
t = 1
print(p < t)       # False

Boolean Operators

Python provides three logical operators: and, or, not, they are used to construct more complex expressions.

The Truth Tables:

• and: if both are True, the result is True True and True------ True True and False----- False False and True----- False False and False----- False

• or: True if either of the two Boolean values is True. True or False ----- True False or False----- False

• not: operates on only one Boolean value (or expression). Result is the opposite. not True----- False not False --- True

Example

print(False and True)        # False
print(4==2*2 and 2==3)        # False
print((5<10) or ( 10 >= 5*2) )  # True

print('Cat'=='Dog' and not (6==8 or 3==3))
     # False
     # F and not(F or T), this is F and F--> F

While these are all interesting and puzzling, what't the point to keep comparing cats and dogs, let's move on to next lesson, Making Decisions!