1. Python
Let’s get started!

2. Getting Started Two modes: Interactive
Script ** we will be working in script mode for the most part

3. Running a program Open IDLE File  New Window
File  Save (add “.py” to your file, it may not add it automatically)
Run  Run Module

4. Functions
A “function” is a pre-written code that will perform a specific task
Python comes with a number of pre-written functions, but you can also write your own (as we will later on in this class)
Functions begin with a keyword and are followed by a set of parentheses
Ex: print ( )

5. Functions
Functions can pass what we call “arguments”, which are placed inside the parentheses of the function
Ex: print (“Hello, world!”)
Different functions will expect different types of arguments (more on types of arguments later)
When you use a function on python, we say we are “calling” a function

6. Types of Data
There are three types of data that we will use in Python for our purposes
Strings: textual data
Integers: numerical data, restricted to integers
Floats: numerical data, decimals included

7. Strings A string is data that is textual in nature
Strings can contain none or some characters
“String literals” are strings defined within your program/function and must be “delimited” by a special character which tells Python to treat it as textual data, and not as a function
Ex: print (“Hello, world!”)
Ex: print (“print”)

8. Delimiters Python recognizes three types of delimiters
The single “tick” : ( ‘ hello ’ )
The single “quote” : ( “ hey there! ” )
The triple quote : ( “”” what’s up dude “”” )

9. Print Challenge Hello, my name is Bruce! Hi, Bruce!
Try to write a Python program that prints the following lines of text:
Hello, my name is Bruce!
Hi, Bruce!
Fish are friends, not food!

10. Print Challenge Bruce asked, “When was the last time you had fish?”
Now try these:
Bruce asked, “When was the last time you had fish?”
He’s leading an FEA group.
FEA stands for “Fish Eater’s Anonymous.”

11. Print Function
You’ll notice that the print function will automatically add a line break after it prints your argument
“”” the triple quote delimiters can be used for data that is on multiple lines

12. Printing multiple arguments
The print function can accept none or multiple arguments at a time
Multiple arguments can be separated by a comma
Example: print (“Hello!”, ‘my name is’, “Donald”)
The print function will automatically insert a space between any two arguments (we will learn how to avoid this later on)

13. Commenting your program
As we mentioned, your programs can become very long, so you will want to write comments either for yourself or another user
Python recognizes the symbol # as a commentator symbol, so it will ignore everything that comes after that symbol on the same line
# First, I will ask the user for their name, I will then store it in a variable called “x”
x = input (“What is your name?”)
# Now, I will print the name of the user
print (x)

14. Multi-line comments
You can also input multi-line comments on Python using the triple quote delimiter
“””
Python will ignore this line
And this line
And this one too
print (“Hello, world!”)

15. Comments as Pseudocode
Comments are often used as pseudocode in order to outline the task at hand
Ex:
#get two test scores from user
# add test scores
# divide by 2
# print out result

16. Comments as a debugging technique
Comments can be used for debugging because Python will ignore portions of your code
Debugging means to identify and to remove any errors in your code
# I don’t know why this one isn’t working!
# print ( ‘ Hello, world! ” )

17. Variables
Variables are like buckets that hold and store information in your computer’s memory
You can create a variable by using the following syntax:
variablename = data
Examples: speed = 5
name = “Donald”
The “=” is the assignment operator and it tells Python to store data on right of operator into variable, named on the left of the operator

18. Rules on naming variables
You cannot use reserved words (they are listed on the next slide)
Variable names can’t contain spaces but they can contain an underscore “_”
The first character of a variable name must be a letter or an underscore, it cannot be a numerical value
Python is case sensitive (variablename vs. VariableName)

19. Reserved words These words cannot be used as variable names:
False, True, None, and, as, assert, break, class, continued, def, del, elif, else, except, finally, for, from, global, if, import, in, is, lambda, nonlocal, not, or, pass, raise, return, try, while, with, yield
(you’ll notice, True, False, None have capital letters)
Reserved words will show up in a different color while writing in script mode

20. Examples
class = 2 Class = 2 classAvg = 24 _class_avg = 42 2ndclassAvg = 56 classavg! = 99

21. Examples
class = 2 illegal (reserved word) Class = 2 legal classAvg = 24 legal _class_avg = 42 legal 2ndclassAvg = 56 illegal (can’t start with a number) classavg! = 99 illegal (only alphanumeric values, and “_” )

22. Common Variable Naming Techniques
Some variable names can be hard to read, so there are common techniques that are used to distinguish them:
cartopspeed = # hard to read …
car_top_speed = 140
carTopSpeed = 140
car_top_speed_3 = 140

23. Printing variables
You can print the data that is stored within a variable by passing the variable as an argument into the print function
name = “Donald” name = “Donald”
print (name) print (“Hello, my name is”, name)
>> Donald >> Hello, my name is Donald

24. Changing variables
Variables are called variables because the data stored in them can be changed
You can change the value/data stored in a variable with a second assigning statement
dollars = 19.99
print (“I have”, dollars, “in my account”)
dollars =
print (“Now, I have”, dollars, “in my account”)

25. Multiple Assignments
You can assign multiple variables on the same line:
x, y, z = 1, 2, 3
# the variables will assume the values in order
You can also assign the same value to multiple variables
x = y = z = 10
# variables x, y, and z will all hold the value of 10

26. Practice
You’re working on a simple inventory management system for a small store. You’d like to store the name and price of two products and print them, so that your inventory page looks something like this:
Item: Bread, price: $ 1.99
Item: Eggs, price: $ 3.49