Types, Truth, and Expressions

Types, Truth, and Expressions Intro to Computer Science CS1510 Dr. Sarah Diesburg

Homework Hints • From now on can use CONSTANT_NAMES for constants • No line wrap

Observations from PA 1 • Variable names matter (don’t call it startingMileageStr when it contains a number) • Why would you import math? • Why would you say float(2.2) • Do your own work!

Questions about PA02??

Line Wrap • Some rules • Strings must be closed in the line in which they start • Adding a backslash at the end of the line tells python that the command is continued on the end of the line

Review : Python if Statement if <expression> : suite • Evaluate the expression to a boolean value (True or False) • if True, execute all statements in the suite

Review : Warning About Indentation • Elements of the “suite” must all be indented the same number of spaces/tabs • Python only recognizes suites when they are indented the same “distance” • You must be careful to get the indentation right to get suites right.

Let’s test your knowledge • Let‘s look at #1-4 in my questions.py program…

Let’s test your knowledge • Problems #1-4 : Which letters are printed? • A • B • A and B • Neither

Let’s test your knowledge • Let’s look at statements with if, elif, else • Problems #5-9 : Which letters are printed? • A • B • A and B • Neither

Python Selection, Round 2 if boolean expression: suite1 else: suite2 The process is: • evaluate the boolean • if True, run suite1 • if False, run suite2

Python Selection, Round 3 if boolean expression1: suite1 elif expression2: suite2 The process is: • evaluate expression1 • if True, run suite1 • If False, evaluate expression 2 • if True, run suite2

Python Selection, Round 3 if boolean expression1: suite1 elif boolean expression2: suite2 #(as many elif’s as you want) else: suiteLast

if, elif, else, the Process • Evaluate boolean expressions until: • The boolean expression returns True • None of the boolean expressions return True • If a boolean returns True, run the corresponding suite. Skip the rest of the if • If no boolean returns True, run the else suite, the default suite

Types, Truth, and Expressions