1. ECS15
boolean

2. Boolean expressions Have value True or False Examples: answer == “b”
2+2 == 4
2+2 == 5
“cat” != “Cat”
x= 5
x==5
x!=5
answer == “b”
x < 30
2+2 == 4
2+2 == 5
“cat” != “Cat”

3. Comparison Operators ==; ‘a’==“a” !=; ‘a’!=“A”; 4!=5 >= <= <

4. Boolean algebra Named after George Boole (1815-1864)
Main idea: you can write down logic as mathematical formulas, as well as in sentences.
Logic as a computational system. Python does some of this computation!
>>> 2+2==4 and 2+1 ==3
True
>>> 2+2==4 and 2+1==4
False
>>> 2+2==4 or 2+2==5
>>> 2+2==4 or 2+1==3
>>> not 2+2==4
>>> not 2+2==3
>>>

5. and True if both are true True and True == False and True ==
False and False ==
True and False ==
>>> 2+2==4 and 2+2==5
False
>>> False and True
>>> True and False
>>> True and True
True
>>> False and False
>>>

6. and True if both are true True and True == True
False and True == False
False and False == False
True and False == False
>>> 2+2==4 and 2+2==5
False
>>> False and True
>>> True and False
>>> True and True
True
>>> False and False
>>>

7. Or True if one or the other is true True or True == True or False ==
False or True ==
False or False ==
>>> "cat"=="cat" and "cat"=="dog"
False
>>> "cat"=="cat" or "cat"=="dog"
True
>>> False or True == True
>>> False or True == False

8. Or True if one or the other is true True or True == True
True or False == True
False or True == True
False or False == False
>>> "cat"=="cat" and "cat"=="dog"
False
>>> "cat"=="cat" or "cat"=="dog"
True
>>> False or True == True
>>> False or True == False

9. Not not True == not False ==
>>> True and (False or not False)
True
>>> False or not False and False
False
>>> False or not (False and False)

10. Not not True == False not False == True
>>> True and (False or not False)
True
>>> False or not False and False
False
>>> False or not (False and False)

11. Operators and, or and not are Boolean operators
Addition is a numeric operator
2+2
Concatenation is a string operator
“drive”+”way”

12. In if statements if reply != “a” and reply != “b”:
print (“Please answer a or b”)
if reply == “a” or reply == “b”:
print (“Thank you!”)