Lecture 4: More Variables Operators and Operands Code Execution ..., Schemes and Mind Maps of Web Programming and Technologies

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CSCI 141

Lecture 4:

More Variables

Operators and Operands

Code Execution: Statements and Expressions

Announcements

One small syllabus change:

1. Previously: drop up to 9 missed poll questions. Now: poll questions are batched by day; drop up to 3 days of missed polls.

Announcements

QOTD

What does the following code print? print ( int (3.91))

Which of the following programs does not print the same thing as the others? a = 14 b = 3 print (a, b) a = 3 b = 14 print ( 14 , 3 ) a = 14 b = a print (a, b) a = 3 b = 14 print ( 14 , a)

A: B:

C: D:

QOTD

Which of the following programs does not print the same thing as the others? a = 14 b = 3 print (a, b) a = 3 b = 14 print ( 14 , 3 ) a = 14 b = a print (a, b) a = 3 b = 14 print ( 14 , a)

A: B:

C: D:

QOTD

Which of the following programs does not print the same thing as the others? a = 14 b = 3 print (a, b) a = 3 b = 14 print ( 14 , 3 ) a = 14 b = a print (a, b) a = 3 b = 14 print ( 14 , a)

A: B:

C: D:

QOTD

Goals

• Understand how to use variables in assignment statements and elsewhere in place of values
• Know the rules for naming variables, and the conventions for deciding on good variable names
• Know how to use the^ sep, and^ end^ keyword arguments with the^ print function.
• Know the definition and usage of operators and operands
  • Know how to use the following operators: =, +, -, *, **, /, //, %
• Understand the distinction between a statement and an expression.
• Understand function calls as expressions that evaluate to their return values.

• Assigning a value is not stating an equality, like in math: it’s storing a value. A variable’s value can be updated (overwritten) by a new value using the assignment operator. Last time: How to read an assignment statement my_age = 31 my_age = 32 “my_age equals 32” “my_age becomes 32” “my_age gets 32” “the variable my_age takes on the value 32”

• Assigning a value is not stating an equality, like in math: it’s storing a value. A variable’s value can be updated (overwritten) by a new value using the assignment operator. Last time: How to read an assignment statement my_age = 31 my_age = 32 “my_age equals 32” “my_age becomes 32” “my_age gets 32” “the variable my_age takes on the value 32”

• Assigning a value is not stating an equality, like in math: it’s storing a value. A variable’s value can be updated (overwritten) by a new value using the assignment operator. Last time: How to read an assignment statement my_age = 31 my_age = 32 “my_age equals 32” “my_age becomes 32” “my_age gets 32” “the variable my_age takes on the value 32”

• Assigning a value is not stating an equality, like in math: it’s storing a value. A variable’s value can be updated (overwritten) by a new value using the assignment operator. Last time: How to read an assignment statement my_age = 31 my_age = 32 “my_age equals 32” “my_age becomes 32” “my_age gets 32” “the variable my_age takes on the value 32”

Variable Names

Variable Names

How do you use variables?

1. Decide what value you want to store in the variable 2. Decide on a sensible name
2. In your program, use the assignment operator to store that value in the variable