Download How are variables set up and used in programming?

Student objective: How are
variables set up and used in
programming?
Bell ringer: Where we using python
in the interactive mode or script
mode on Friday?
Set Up Grade Sheet
•
•
•
•
•
•
•
KWL (5)
Syllabus (5)
Communication compact (5)
Computer Parts Project (25)
Vocab (10)
Print Project (10)
Number Guessing Game (10)
Agenda
• Notes on python basics and variables
• Assignments: programming
Bell Ringer Answer: Interactive
Interactive mode-program and run in IDLE
• Immediate feedback
• Not designed to save and run later
Script Mode Write the program
• Write program and save it to use later
Let’s try it
•
•
•
•
•
To write a python program and save it:
Open Python IDLE
Click on file—New Window
Type your program in
File—Save as .py in documents folder of
python
• Click Run—Run Module
• IDLE pops back up with program
Syntax Errors
• Spelling/grammar
• Picked up prior to running program
Runtime errors
• Occur during execution of program
• 4-line error message starting with Traceback
• Tells where the error is and what it is
Semantic errors
• Don’t use commas with numbers or will get
this error
• Code will run but be wrong
Computer
• Input
• Processing
• Output
Variables
Variables (values)
• Integers: int
numbers no decimal points
• Strings: str use single or double quotation
character or string of
characters: letters, numbers,
punctuation
• Long string: str multi-line string: triple
quotes
• Floating point: float decimal numbers
Color coding
•
•
•
•
Special words, like print: orange
Strings: green
Output: blue
Comments: red
Comments
•
•
•
•
Used to explain code
Invaluable to programmers
Are not executable by the computer
# symbol is used to denote the start of a
comment
Blank Lines and Spacing
Blank lines
• Are ignored by the computer
• Can make program easier to read
Spacing
• is critical and will create errors if not followed
• Tells where blocks of code start and where they
stop
• Convention: 4 spaces in
• Necessary for if statement
Naming Variables
• If you don’t know the type of variable, you can find out by
• Writing in the IDLE:
• type ( variable ) then click return (Remember strings in
quotes, numbers not)
• You can name variables (words, numbers) to input into
memory (Name it so you can use it)
•
• Teacher = “Mr. Morton”
• First = 5
• *You can have more than one name for one thing
• *You can also change names
Rules for naming variables:
• Can use letters, numbers and underscore
character(_)
• Case sensitive
• Must start with letter or underscore (Not a
good idea to start with underscore), NOT A
NUMBER
• Make variables names clear—don’t try to
abbreviate
Concatenate:
• Adding strings like “cat” + “dog”
• Results would be catdog
Using variables
•
•
•
•
•
•
•
•
•
Variables can also be made to equal themselves:
>>Score = 7
>>Score = Score
>>Score = Score + 1
>>print Score Hit return
Generates >>8
Useful to increment or decrement a value