Python for Physical Science.pdf

Python 3 for
Physical Science
M. Anderson & M. Tellez

Python and
Programming
Languages

Programming Languages
A Programming Language is the set of rules that provides a way of telling a
computer what operations to perform. This is done by translating an algorithm
(series of steps to solve a problem) into the linguistic framework provided by the
programming language.
A programming language provides a human-readable form to communicate
machine-readable instructions.

Types Programming Languages
High-Level Language
1. It is programmer-friendly language.
2. It is easy to understand.
3. It is simple to debug.
4. It is simple to maintain.
5. It can run on any platform.
6. It needs compiler or interpreter for
translation.
7. Examples: Java, Python, Objective
C, Swift, C++
Low-level Language
1. It is a machine-friendly language.
2. It is difﬁcult to understand.
3. It is complex to debug
comparatively.
4. It is complex to maintain
comparatively.
5. It is machine-dependent.
6. It needs assembler for translation.
7. Examples: Assembly language and
machine language.

Why Python
- Python is an open source programming language
- Free
- Python is ﬂexible and intuitive
- Plenty of available Python libraries and resources online
- Python is good for beginners and great foundational language
- Closer to human/natural language
- Python is a current and commercial language.
- More than just an academic exercise. Students can apply their learning in real industry.
- Python can be used for
- AI
- Web/Mobile Development
- Data Analysis and Visualization
- Desktop GUIs

9th grade goals for Computer Science
Programming Fundamentals: These are
foundational concepts of programming that
can be easily translated in another
programming language and that are
necessary to fully understand for a
programmer to reach higher levels of
complexity
- Sequencing
- Variables
- Input and Output
- Selection
- Repetition
- Data Structures
Computational Thinking: This is the
underlying set of ways of thinking that
are necessary for computer scientist to
solve complex problems.
Computational thinking can be
improved by programming. The main
pillars of computational thinking are:
- Decomposition.
- Pattern recognition
- Abstraction
- Algorithmic thinking.
*more info here

PyCharm
❏ IDE: Integrated Development Environment.
❏ Software to write, compile (translate into machine code), debug and test your
programs.
Goal
❏ Get familiar with the PyCharm environment

First time
PyCharm
Installation

1. Sign-up to Jetbrains for free licenses
1. Go to
https://www.jetbrains.com/community/education/#st
udents
2. Scroll down to ﬁnd the “Apply now” button
3. Complete the form for Products for Learning
4. Conﬁrm your account in your school email.
Use school email account
SIGN UP FIRST! DON’T DOWNLOAD THE FREE PYCHARM VERSION

2. Download licensed Pycharm IDE
1. Login to https://account.jetbrains.com/login using
your school google account
2. Download Pycharm IDE
1
2
3

3. Install PyCharm
1. Drag and drop PyCharm to
Applications folder
2. Follow the prompts to completely
install the program

4. Activate PyCharm
1. Open your PyCharm
2. PyCharmActivate
3. Click “Log in to Jetbrains
Account to authorize”
4. On PyCharm, Click Activate
5. You should see “Authorization
Successful” conﬁrmation

4. Successful Installation
This is the screen you should see if
PyCharm was successfully
installed.

5. Download and Setup Python Interpreter
1. Download Interpreter from
here
2. Install the interpreter
downloaded
END
of HW

Second time
Pycharm
installation for
new computers

Installing PyCharm for students who got a new computer
Interpreter
1. Download the Python Interpreter by clicking the yellow button
https://www.python.org/downloads/
2. Install the Python Interpreter until ﬁnished
PyCharm
3. Login to your Jetbrains account https://account.jetbrains.com/licenses
4. Download the PyCharm from the list JetBrains Product Pack for Students
5. After downloading, open, drag and drop the Pycharm app to the Applications folder and follow the
prompt until installation is complete.
6. Open the installed Pycharm, you should be good to go

We Do #1
- Create a new Project
- Create your ﬁrst Python
program: “Hello Physical
Science”
On your PyCharm

Create a new project
1. Click New Project

2. Check Interpreter
❏ Choose the “Pure Python”
option
❏ Name your project “Unit1”
using camel notation (capital
initial letter for every word, no
space in between)
❏ If you don’t see a Base
interpreter, refer back to step 5
of the installation process.

Python Files Fundamentals
❏ A Python Project can contain one or more
packages. These are simply folders to
organize your programs*.
❏ A package can contain one or more
Python Files.
❏ Python File can hold all the instructions
needed for a program.
These instructions are normally broken
down into multiple functions

Create a Python Package
❏ Right click on the Project
(Folder)
❏ Select “New”
❏ Select “Python Package”
❏ Name the new package
“variablesAndFunctions”

Create Python File
- Right-click on the
package
- Create a Python File
- Name it: HelloPS
(camelStyle)

Quick PyCharm IDE* Orientation
Project
navigation
Output
window
Editor window
Debugging and
VCS tools
*“Integrated Development Environment”

Code your first program
- Type the instructions you wish
to add to your program on the
editor window:
print(“Hello Physical
Sciences”)
- Right click the file, and choose
Run to compile and execute
your program.
- If you see “Hello Physical
Sciences” in your output
window, your first program is
running!

Code Comments
❏ Comments in code refers to lines of text that are excluded from compilation (not executed by the
compiler) and are used to document your code. Proper code documentation is fundamental to be
able to share, maintain, and reuse code
❏ In Python a inline and single line comment is created by using the character # before your
comment (use a space before and after the #)
❏ Multiple line comments can be created using three quotation marks at the beginning and end.

Unit 1:
Output, Variables,
Input, Operators
and Functions

Variables and Output with Built-in Functions
Variables are containers for storing data
values.
❏ Variable names are case sensitive
❏ a, b, c, A, d are different variables
❏ “=” is an assignment operator
❏ 5, “John”, 24.5, 4 are values
assigned to the variables
❏ print() is a built-in function
❏ type() is a built-in function -
(optional) use the type() function
to determine the type of data
assigned to a variable
a = 5
b = "John"
c = 24.5
A = 4
d = True
print(a) # prints 5
print(b) # prints John
print(c) # prints 24.5
print(A) # prints 4
print(type(a)) # prints class int
print(type(b)) # prints class str
print(type(c)) # prints class float
print(type(A)) # prints class int
print(type(d)) # prints class bool

Output in Python - print() function
print("Wow! " + "Python is cool!")
print("Hello", end=' ')
print("Physicists!")
print("Good night", "Chemists", sep=", ")
print("Jeff's last name is Clark")
# concatenation (add text together)
# keeps the following print on the
same line
#prints adding a separator in
between each text
#the backslash () allows you to print
characters that are language reserved
(‘)

Output in Python - print() function
var = “Science is fun!”
print("Wow! ", var)
force = 5
force_unit = “N”
print(force, force_unit)
# Print multiple things by separating
them with a comma. We are printing
a variable and a string here.
What would print here?
# Prints two variables. What types of
variables are these?

DISCUSSION
What is similar and different between the term “variable” in Python and Science?

You Do
❏ Create 3 variables (name,
height, height_units) for your
data
❏ Print your info using text and
variables (see example on the
left)
END
of
Lesson

Arithmetic Operations
print(8 - 2)
print(4.5 + 3)
print(7 / 2)
print(7 // 2) # integer division
print(7 * 3)
print(7 % 3) # modulo
print(2 ** 3) # exponent
# subtraction with two integers
# subtraction/addition with ﬂoat and integer
# division (real division)
# integer division (truncates the decimal portion)
# multiplication
# modulo (remainder operator)
# exponent

OPTIONAL: Compound Assignment Operators
Operator Example Equivalent
+= a += 1 a = a + 1;
-= a -= 1 a = a - 1;
*= a *= 2 a = a * 2;
/= a /= 2 a = a / 2;
//= a /= 2 a = a // 2;
%= a %= 2 a = a % 2;
**= a **= 2 a = a ** 2;

Trace the changing values of x
x = 0
print(x)
x += 1
print(x)
x += 2
print(x)
x *= 4
print(x)
x /= 2
print(x)
x %= 5
print(x)
#
#
#
#
#
#

print() function (continuation)
a = 4
b = 2
print("Sum: ", (a + b))
print("Difference: ", (a - b))
print("Product: ", (a * b))
print("Quotient: ", (a / b)
print("Remainder: " + str(a % b))
You can concatenate text and variable
values with operations together on
print statements.
You can print a text and then a
number separating them with a
comma/s.
You can convert the number to a
text casting to String using str()
built-in function

You Do:
Age and Height
❏ Create 3 variables (Name, Year
of birth, height)
❏ Print the info using text and
variables
❏ Calculate and print your age
❏ Calculate and print your your
height difference from 1.7 m
Sample Solution (teachers only)

Built-in Functions (print, input)
You’ve already been using built-in functions! The print function to print a string
- print(“Hello Physical Sciences!”)
Other built-in function: input allows you to get user input. The program will
wait for input and store it on the variable movie.
- movie = input(“What is your favorite movie?”)

Built-in Functions (print, input, int)
PROBLEM - inputs default as text (strings)
This means Python assumes that anything a user inputs is text, not a number
EVEN IF IT’S A NUMERIC DIGIT (e.g. “4”)
- force = input(“What is the force? “)
- print(force * 2)
…causes an ERROR because it thinks the force is text
and you can’t do math with text
The int function to change from one data type to another data type (integer)
- force = int(input(“What is the force? “))
- print(force * 2) ← SUCCESS

Built-in Functions (print, input, int)
Optional for later
Here are some other useful built-in functions:
❏ round(float, int) - rounds ﬂoat to int decimal places
❏ max(arg1, arg2, argN) - gets the maximum value of arguments
❏ min(arg1, arg2, argN) - gets the minimum value of arguments
❏ len(s) – gets the length (number of items) of an object s
For reference: https://docs.python.org/3/library/functions.html

We Do
Expected output
Enter length:
Enter width:
Area:
Perimeter:
Create a Python program that reads and stores a rectangle’s
length and width and calculate and outputs the area and
perimeter of a rectangle
*note: Your input needs to be cast as a integer before you are able
to do operations.
number = int(input(“Enter a number: “))

You Do - Velocity
Write a Python program to store
the values of distance and time
and calculate and print the
velocity.
Enter distance:
Enter time:
Velocity is:

You Do -
Distance/Time
Write a program that will read the
velocity of an object and will output
the distance traveled at 5 constant
intervals of time.
END
of
Lesson

What is a function?
❏ A function is a block of organized, reusable code
that is used to perform a single, related action
❏ A function provides modularity for your
applications and a high degree of code reuse
❏ Python provides built-in functions which are part
of the core language.
❏ Python allows you to deﬁne your own
(user-deﬁned) functions
❏ Functions can be called several times allowing for
the same set of statements to be executed without
repeating code.
TimerApp
showTimer()
startTime()
pauseTime()
stopTime()
resetTime()
QuizApp
showInstruction()
startQuiz()
showQuestion()
showChoices()
showTimer()
Physics Quiz
Instructions
Start Quiz
Time:

Conventions of user-deﬁned functions
● Functions have conventions
a. Name a function based on what it does (in lowercase (no camel) - python)
b. Whitespace/indentation is important!
c. Function body “code blocks” (groups of statements) are indented (4 spaces or tab)
● Sometimes a function takes values from outside through variables enclosed
in parenthesis called parameters.
a. When you call (or use) the function, you pass arguments as values to the parameters
● Sometimes a function returns a speciﬁc value through a return statement,
prints a value using the print function, and/or not return or print at all.

User-defined function
❏ In Python, a user-defined function declaration begins with the keyword def followed by the
function name.
❏ The function may take arguments(s) as input within the opening and closing parentheses, just
after the function name followed by a colon.
❏ After defining the function name and arguments(s) a block of program statement(s) start at the
next line and these statement(s) must be indented.
❏ To end a function you must leave two empty lines after the last statement.
❏ A function can return a value by using the keyword return
def function_name(argument1, argument2, ...) :
statement_1
statement_2
return…(optional)

A closer look at a Python function
def function_name(argument1, argument2, ...) :
statement_1
statement_2
return…(optional)
Python keyword to
define a function
function name
(arbitrarily named)
variable/s to hold the value/s sent
to the function to perform its task
code/s that work together to
perform a task

User-deﬁned Function
Function that return (s)
This function square() has a single parameter,
squares the argument, and returns the result
def square(x):
y = x * x
return y
When we call the square function, we pass 10 as
an argument. We store the value that is returned a
variable result, and print it
to_square = 10
result = square(to_square)
print(result) # 100
print(square(5) + 1200) # 1225
Void (non-return) Function
Function square() takes one argument, squares
the argument, and prints the result
def square(x):
y = x * x
print(y)
When we call the square function, we pass 10 as an
argument. In this case we won’t have access to the result
of the operation.
to_square = 10
square(to_square)
print(square(5) + 10) # cause an error
square(2) # 4

We Do [5 minutes]
Rectangle Functions
Expected output
Enter length: 2
Enter width: 4
Area: 8
Perimeter: 12
Create a Python Rectangle program that
includes 2 functions that allow for length
and width to be passed as arguments,
calculate the area and perimeter, and
returns the result.

You Do - Velocity
Function
Create a Python ﬁle with a function that
allows for passing distance and time as
arguments and returns the velocity.
Make sure you are using a function to
determine the velocity.
Enter distance in m:5
Enter time in s: 2
Velocity in m/s: 2.5
END
of
Lesson

Scope of a variable
❏ When utilizing functions it is important to understand the scope (or lifetime) of any variable.
❏ Variables created within a function are local to that function and cannot be accessed outside of it.
❏ Variables created outside a function are known as global and can be accessed inside of functions.
def local1():
spam = "local spam" # local variable
print("Local printing:", spam)
def local2():
spam2 = "local spam2" # local variable
spam = "test spam" # sets a variable with global in scope
local1() # calls the local1 function
print("After local assignment:", spam) # uses the global variable
print("Attempt to access local:", spam2) # causes a name error because spam2 is not defined
The output of the example code is:
Local printing: local spam
After local assignment: test spam

Scope of a variable
def function1():
local_variable = "ONLY IN the function"
print(local_variable) # prints the variable inside the function
global_variable = "EVERYWHERE in the program, including functions”
print(global_variable) # uses the global variable
print(local_variable) # error, local_variable doesn’t exist outside of the function

You Do
Moving Object
Complete the following Python
project
Work with someone (code
independently)
END
of
Lesson

Submit your Python Program
in 2 steps

1. On PyCharm
1. Right click on the ﬁle (.py)
you want to submit
2. Choose >> Open In
3. Choose Finder

2. On Finder Window
1. You should see the Python
file you selected to submit
on the finder window
2. That is the file you will drag
and drop to the submission
bin on Google classroom

Loops and for loop
❏ Loop structure that executes
a set of statements a ﬁxed
number of times
❏ for loops
❏ Run a piece of code for
a given number of
times
for loop flowchart
start
last
item?
end
statement
try next item
yes
no

for loop
for n in range(5):
print(n)
Initialization - n is a loop
control variable that represents
every number in a range
starting at a default value of 0
range()- function to specify
where to end the loop. Ends
before the specified value
Update step - by default n will
increment by 1
Loop body - what needs to be
done

for loop and the range() function
def printNums(num):
for n in range(num):
print(n)
n = int(input("Enter a number: " ))
printNums(n)
What is the output of the
code segment if n is 2?
❏ Use the range() function to loop through a set of statements
❏ The range() function returns a sequence of numbers, starting from 0 by default,
and increments by 1 (by default), and ends before the specified number as
parameter of the function.
❏ Inclusive of 0, exclusive of the argument/parameter specified

Looping from a different start value
for n in range(2, 12):
print(n*2) What is the output of the
code segment?
❏ To loop from another starting value other than 0, specify the starting value
by adding a second parameter:
range(2, 6), which means values from 2 to < 6 (excluding 6):

Looping and using a different value to increment other than 1
for n in range(2, 30, 3):
print(n)
# to place the next item to be printed on the
same line after the space
2
5
8
11
14
17
20
23
❏ The range() function defaults to increment by 1
❏ To specify another increment value other than 1, add a third parameter:
range(2, 30, 3):

Looping and using a different value to increment other than 1
for n in range(2, 30, 3):
print(n, end=" ")
# to place the next item to be printed on the
same line after the space
2 5 8 11 14 17 20 23 26 29
❏ We can change the way the print function ends, using “end”
❏ Print default is to end with a hidden new line (script=“n”). We can
change it to just a space using end=" "

We Do
Create a Python program called OddsEvens with 2
functions called printOdds and printEvens.
The printOdds function prints all the odd numbers
from zero (0) to the number passed to the parameter.
The printEvens function uses 2 parameters to set
the start number and the end number, then prints all
even numbers on one line, from start number to end
number passed to the 2 parameters.
The program output should look like this:
Odd numbers from 0 to n
Enter value of n: 4
1
3
Even numbers from n1 to n2:
Enter value of n1: 2
Enter value of n2: 6
2 4 6

You Do
Allow the user to input a force and a mass of
an object.
Make a program that prints (using a for loop)
the work done on the box after each meter
and the velocity of the object.
Print these values for the ﬁrst 5 meters.
(Advanced option, allow the user to input the
max distance and the distance increment)
Work = F * D
KE = 0.5 * mv2

Looping through a String
for x in "physics":
print(x)
p
h
y
s
i
c
s
❏ You can iterate through a string value
❏ A string contains a sequence of characters.
❏ The loop control variable represents each character in the string

Random Numbers
❏ To generate a pseudo-random number in Python you need to import the random module to use
the Python random built-in functions
import random
print(random.random()) # Random float: 0.0 <= x < 1.0
print(random.uniform( 2.5, 10.0)) # Random float: 2.5 <= x <= 10.0
print(random.randrange( 10)) # Integer from 0 to 9 inclusive
print(random.randrange( 0, 101, 2)) # Integer from 0 to 100 inclusive

1. On PyCharm
1. Right click on the ﬁle (.py)
you ant to submit
2. Choose >> Open In
3. Choose Finder

List
❏ Lists are used to store multiple items in a single variable.
❏ Lists are created using square brackets [ ]
❏ The list is changeable, meaning that we can change, add, and remove items in a list after it has been
created.
❏ The elements in a list are indexed in deﬁnite sequence and the indexing of a list is done with 0
being the ﬁrst index and the last index is at len(list) - 1.
❏ Structure:
fruits = ["apple", "banana", "cherry"]
print(fruits)
0 1 2 index numbers
Prints items in list

Create a list with different types of items
❏ Create a list with random strings
someList = ['1', 'dog', 'cat', '789']
❏ Print the list
print(someList)
❏ Get the length of the list
print(len(someList))
❏ Get the 2nd item in the list
print(someList[1])
❏ Get the 5th item in the list
print(someList[4]) #Note: this doesn’t exist. This will cause an error

Adding and removing items from List
❏ You can add items to a list
someList.append('banana')
❏ Remove items from a list
someList.pop() #Removes the last item from list
print(someList)
someList.pop(2) #Removes the 3rd item from list
print(someList)
❏ Check if an item is in a list
print('dog' in someList) #checks if dog is in list

Looping through a list
velocity = [23, 32, 45]
for x in velocity:
print(x)
List velocity with 3 items
For every item x in list velocity
prints each item x
Output
23
32
45

Looping through a list
velocity = [23, 32, 45]
for x in velocity:
print(x, end=" ") 23 32 45
❏ The elements in a list are indexed in definite sequence
and the indexing of a list is done with 0 being the first
index and the last index is at len(list) - 1.
velocity = [23, 32, 45]
total = 0
for x in velocity:
total += x
average = total / len(velocity)
print("Average Velocity: ", round(average, 2))
len() - function that returns the
number of elements in the list
Average Velocity: 33.33
NOTE: By default, the print function
ends with a new line. Passing the
whitespace to the end parameter
(end=' ') indicates that the end
character has to be identified by
whitespace and not a newline.

CodeHS Practice exercises
Use the following sections of the self-paced CodeHS course to review some of the
concepts we have covered:
Variables and Data Types Section 3.2
Section 3.5
Operators / Input / Output
(Built-in Functions)
Section 3.1
Section 3.3
Section 3.4
User-defined Functions Section 6.1
Section 6.2
Section 6.4

Control Flow
Control flow statements allow you to create
alternative branches in the execution of your
program.
They are the foundation of many of the logic
in programming and in Artificial Intelligence
Control flow statements are as good as the
conditional statements that we create to
determine those branches or paths.

Relational Operators
Operator Meaning
== equal (double equal sign)
< less than
<= less than or equal
> greater than
>= greater than or equal
!= not equal
❏ A relational operator is a
programming language construct
that tests or defines the
relation between two entities.
❏ The result of using the operator
will yield one (1) of two (2)
possible boolean outputs (True
or False)
❏ An expression that uses one or
more of these operators is
called a Boolean expression.

If Statements
❏ If statements require a boolean expression to
decide if the following code will be executed.
❏ There can be zero or more elif clauses, and the else
part is optional. The keyword ‘elif’ is short for ‘else
if’. The elif clause requires an additional boolean
statement to create an alternative path.
❏ Only one of the parts on an if..elif..elif..else
statement will be executed
❏ The else part does not require a conditional and
will be executed if none of the previous conditions
are True
def checkX(x):
if x < 0:
print('Negative')
print('This is still the if
')
elif x == 0:
print('Zero')
elif x == 1:
print('Single')
else:
print('More')

We do
Create a letterGrade application that prompts
the user for the percentage earned on a test
or other graded work and then displays the
corresponding letter grade. The application
should use your favorite grading scale
Sample Output:
Enter the percentage: 80
The corresponding letter grade is: B

You Do
Complete the attached python
project on BMI calculation.
Use functions as appropriate
Work with someone

1. Logical operators (not), (and), and (or) are used to form compound boolean
expressions.
2. The table below shows the order these operators will be evaluated by the
compiler.
3. A compound boolean expression will evaluate to a single Boolean value (true or
false).
Compound or complex boolean expressions:
● grade > 70 and grade < 60
● temp > 39 and coughing == true
● tired == true or time >= 21
● not (initialSpeed > 30)
Logical Operators
Operator
Boolean Algebra
equivalent
not ~ (⌐)
and . (⋀)
or + (∨)

Evaluating expressions with Logical Operators
Example 1:
(condition1 and condition2)
Is true if and only if both c1 and c2 are true
Example 2:
(condition1 or condition2)
Is true if c1 or c2 or both are true
Example 3:
not(condition1)
Is true if and only if c1 is false

Truth Tables (AND, OR, NOT)
If both conditions are true, the output
is true. Otherwise, false
and
X = (A and B)
A B X
False False False
False True False
True False False
True True True
If both conditions are false, the output
is false. Otherwise, true
or
X = (A or B)
A B X
False False False
False True True
True False True
True True True
The output is the
reversed of the input
not
X = not A
A X
False True
True False

Truth Tables (XOR, NAND, NOR)
The output is true if either one
condition or the other is true.
Excluding the case that they both are
XOR Exclusive OR
X = (A ^ B)
A B X
False False False
False True True
True False True
True True False
The reversed of AND
NAND
X = not(A and B)
A B Output
False False True
False True True
True False True
True True False
The reversed of OR
NOR
X = not(A or B)
A B Output
False False True
False True False
True False False
True True False

We do
What is printed after executing
the given code segment?
a = True
b = False
c = a and b
d = a or b
e = not b
f = a ^ b
g = not(a or b)
h = not(a and b) or b
print(c)
print(d)
print(e)
print(f)
print(g)
print(h)

You Do
Write a program that asks for the atomic number of
an element and returns the number of valence
electrons and the ion charge
Notes:
Ensure the atomic number (atno) is between 1-20
Elements with atno <= 2 (Helium)
have valence electron equal to atno
Elements with atno <= 10 (Neon)
have valence electron equal to atno - 2
Elements with atno <= 18 (Argon)
have valence electron equal to atno - 10
Elements with valence <= 4 have equal valence and
ion charge
Elements with valence > 4 have ion charge equal to
valence - 8

CodeHS Practice exercises
Use the following sections of the self-paced CodeHS course to review some of the
concepts we have covered:
Variables and Data Types Section 3.2
Section 3.5
Operators / Input / Output
(Built-in Functions)
Section 3.1
Section 3.3
Section 3.4
User-defined Functions Section 6.1
Section 6.2
Section 6.4
Selection statements (if) Section 4.1 - 4.6

Python Class
❏ Python is an object-oriented-programming language.
❏ Almost everything in Python is an object, with its properties and
functions.
❏ Objects are patterned from real-world objects
Read-world object
Attributes
- type
- diameter
Behaviour
- getType
- getDiameter
- getSurfaceArea
- getVolume
Decompose object information
1. Create a Python class
based on object name
2. Create an __init__
function and use the
attributes as parameters
3. Create functions from the
list of behaviour
identified
Translate to program code

WHY???
Why are we doing this? Writing
100 functions is ﬁne with me!
We want to break a bigger program
into smaller manageable
components by
1. grouping information and
functions together for a
speciﬁc object
2. making objects work together
to perform bigger and more
complex tasks

Remember this?
TimerApp
showTimer()
startTime()
pauseTime()
stopTime()
resetTime()
QuizApp
showInstruction()
startQuiz()
showQuestion()
showChoices()
showTimer()
Physics Quiz
Instructions
Start Quiz
Time:
A group of functions
only for the
TimerApp
Another group of
functions for the
QuizApp
Another group of
functions for the
Graphical User
Interface for the user
to interact with

Python Class and Objects
❏ An object consists of :
❏ State: It is represented by the attributes of an object. It also reﬂects the properties of an object.
❏ Behavior: It is represented by the methods of an object. It also reﬂects the response of an object
to other objects.
❏ Identity: It gives a unique name to an object and enables one object to interact with other
objects.
Identity
Name of Ball
State|Attribute
Type
Diameter
Behaviors
● Informs type
● Informs diameter
● Calculates
surface area
● Calculates volume

Writing a Python Class
ClassName
❏ Uses the keyword “class”
❏ A noun, starts with a Capital letter,
then follows a Camel case
Class variables
❏ Indented, aligned with functions
Behavior | Functions
❏ Indented
❏ Starts with def keyword
❏ In __init__ function, add the
instance variables as parameters
class ClassName:
# class/static variable/s
.
.
.
# def __init__(instance variable/s)
# def function1()
# def function2()

We Do
Translate the information of a Ball into a
Python class the following the steps provided.
● Write the class and name it after the
object name
● Write an __init__ function and use
the instance variables as parameters
● Create user-deﬁned functions based on
the behaviour identiﬁed
● Create a runner code
○ Create 3 ball objects of instances
○ Test your code with input values
● Add static variable/s that hold/s a
common value for all objects

Python Class and Objects
❏ An Object is an instance of a Class.
❏ A class is like a blueprint while an instance is a copy of the class with actual values.
❏ You can create many instances or objects from the class template. Without the class as a guide, you
would be lost, not knowing what information is required.
Class Ball
State | Attributes
type
diameter
Behaviors
getType
getDiameter
getSurfaceArea
getVolume
ball1
ball2
ball3
Objects or instance of a class
Class Diagram | Template

You Do #1
Group/Partner
1. Atom
2. Element
With your group
● Identify the attributes of the given object
● Identify the behaviour of the object
● Create a class diagram of the information gathered
● Translate the diagram into a Python class program

Class Diagram of “Atom”
Class Atom
State | Attributes
Name
Atomic Number
Mass Number
Symbol
Behaviors
getName()
getNeutronNumber
getValenceElectrons()
getIonCharge()
atom1
atom2
atom3
Objects or instance of a class
Class Diagram | Template

Parts of a Python Class
class Dog:
# Class Variable
animal = 'dog'
# The init method or constructor
def __init__(self, breed, color):
# Instance Variable
self.breed = breed
self.color = color
def makesound(self, sound):
return sound
# Objects or instances of Dog class
Roger = Dog( "Pug", "brown")
Charlie = Dog( "Bulldog", "black")
print("Breed: ", Roger.breed , " Color: ", Roger.color)
print("Make sound: " , Roger.makesound( "Woof woof" ))
print("Breed: ", Charlie.breed , " Color: ", Charlie.color)
print("Make sound: " , Charlie.makesound( "Zzzzzzzz"))
Class name
Class variables | Static
Constructor/Special function
Instance variables
User-defined method with parameter
sound
Calls the constructor. Creates an
object or instance called Roger of
type Dog and passes “Pug” as value
of breed and “brown” as value of
color (NOTE: All values are only
specific to the instance Roger)

__init__ function and self keyword
❏ __init__ - a special function called a constructor. It is called when an object is created
❏ Constructors are used to initializing the object’s state.
❏ Like functions, a constructor also contains a collection of statements(i.e. instructions) that
are executed at the time of Object creation.
❏ It runs as soon as an object of a class is instantiated.
❏ The function is useful to do any initialization you want to do with your object.
❏ self - is a keyword that indicates that a function is an instance function or variables are
instances of a class.
❏ Class methods must have an extra ﬁrst parameter in the method deﬁnition.
❏ We do not give a value for this parameter when we call the method, Python provides it.
❏ If we have a method that takes no arguments, then we still have to have one argument.

Organizing our runner codes - def main() and if __name__
def main():
length = float(input("Enter length: "))
width = float(input("Enter width: "))
print("Area: ", getArea(length, width))
print("Perimeter: ", getPerimeter(length, width))
if __name__ == "__main__":
main() # calls the main function if it exists
❏ main() function acts as the
point of execution for any
program
❏ The main function is normally
used to control the main
operation of your entire
program. Using sequencing
you normally complete general
tasks such as requesting input,
calling other functions, etc.
❏ The __name__ is a special
built-in variable which evaluates
to the name of the current
module and normally calls the
main() function.

You Do
Create a class Element to deﬁne
periodic table elements.
The class should include name,
atomic number.
Use boolean logic to determine
whether the two atoms would make
a covalent, ionic, or metallic
compound.
Unit 2 Summative Style

while loop flowchart
Loops and while loop
❏ Used to repeat a process
(block of statements) or
perform an operation
multiple times
❏ while loops
❏ Run a piece of code
indeﬁnitely while a
condition is met
start
end
condition statement
true
false
variation

initialize the loop control variable
while condition:
- what happens if condition is true
- changes to control variable
● A variable is created and given
an initial value. Usually a
String, an int or a boolean type
● This variable can then be used as
a loop control variable
● Statements to be executed
when the condition is
true.
● Include a variation to the
control variable to
eventually stop looping
● A condition (boolean
expression) that has to
be true for the loop to
continue.
● It should include the
control variable

Example #1 (while loop)
i = 0
while i < 3:
print(“gum”)
i = i + 1 # or i += 1;
Output ?
declare i (Control
variable)
set i to 0
Continue while i
is less than 3
At end of while
loop,
increase i by 1

while loop example with break keyword
❏ break exits the
entire loop
immediately
❏ What is the output
after running the
code segment?
x = 1
while x <= 10:
if x == 5:
break #this exits the while loop!
print("x is now:", x)
x += 1

The while statement
❏ Loop structure that executes a set of statements as long as a condition is true
❏ The condition is a Boolean expression
❏ Will never execute if the condition is initially false
What does the code segment do?
response = int(input("Enter 1 or 0: "))
while response == 1:
response = int(input("Enter 1 or 0: "))

Example:
Describe what the code
segment does.
password = 'secret'
pw = input('Enter the password: '
)
while pw != password:
print('Password incorrect! Try again.'
)
pw = input('Enter the password: '
)
print("You have successfully logged in!"
)

You Do Allow the user to input an initial
mass and velocity and a frictional
force.
Write a program to print the KE and
Thermal Energy after each meter.
Use a while loop to ensure that the
KE does not go negative.
If the user enters zero for the
frictional force it should instead
print “Never slows down!”

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