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This guide covers the basics of Boolean logic and conditional statements essential for programming. It introduces Boolean values (True and False) and their operations like AND, OR, NOT, equality (==), and inequality (!=). You'll learn how to use Boolean expressions for decision-making in your code, along with if statements and chained conditionals for more complex logic. Additionally, practical coding examples illustrate how to apply these concepts effectively. Prepare yourself for coding assignments and quizzes that involve Boolean logic.
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Selection Victor Norman CS104 Calvin College
Reading Quiz • Counts toward your grade.
New type: bool • Stands for Boolean (named after George Boole) • Two values: True and False • Operations: • and, or, not • equality (==), inequality (!=)
Booleans necessary for “testing” • You “constantly” are making decision: • if something is true, I’ll do this, otherwise, I’ll do that. • Code is similar. • if something < somethingelse: • something < somethingelse is a boolean expression: produces True or False. • if something == 0: • True if something evaluates to the value 0, False otherwise. • Can be used in assignments: • witch = (she == duck) # witch has value True or False.
Boolean operators • <val> < <val> • <val> > <val> • etc: <, >, <=, >=, ==, != Logical Operators: • <booleanValue> and <booleanValue> • <booleanValue> or <booleanValue> • not <booleanValue>
if Statement Syntax if <boolean expression>: <statements: executed if expr is True> if <boolean expression>: <statements: executed if expr is True> else: <statements: executed if expr is False>
Chained Conditionals if <boolean expression>: <statements: executed if expr is True> elif <boolean expression2>: <statements: executed if expr is False and expr2 is> elif <bool expr3>: <statements…> else: # optional! <statements>
Example of use Suppose you have a function called turnDegrees(deg) which takes a positive or negative value in deg. You want to turnLeft() if deg is positive, turnRight() if negative, and do nothing if 0. How would you write this code? if deg > 0: # this code in turnDegrees() turnLeft(deg) elif deg < 0: turnRight(-1 * deg)
Nested conditional Q: Write code that prints the word “odd” or “even” depending on the value of variable anInt, and also prints “greater than 10” if the odd number has a value greater than 10. A: if anInt % 2 == 0 : print "even” else: print "odd” if anInt > 10: print "greater than 10”
Assignment • Do ~60 questions in CodeLab. • Very good practice!
