Introduction to Python - Jouda M Qamar.pdf

Introduction to Python
January 2023
Jouda M. Qamar.
Computer Science - Cairo University

What can Python do?
• Python can be used on a server to create web applications.
• Python can be used alongside software to create workflows.
• Python can connect to database systems. It can also read and
modify files.
• Python can be used to handle big data and perform complex
mathematics.
• Python can be used for rapid prototyping, or for production-ready
software development.
Jouda M.Qamar - 2023 2

What is Python?
• Python is a popular programming language.
• It was created by Guido van Rossum, and released in 1991.
Jouda M.Qamar - 2023
The most recent major version of Python is Python 3, which we shall be
using in this tutorial. However, Python 2, although not being updated with
anything other than security updates, is still quite popular.
______________________________________________
In this tutorial Python will be written in a text editor.
TOOLS:
- python install (https://www.python.org/).
- anaconda (https://www.anaconda.com/).
3

Python Syntax
Python Syntax compared to other programming languages!
• Python was designed for readability.
• Python uses new lines to complete a command, as opposed to other
programming languages which often use semicolons or parentheses.
• Python relies on indentation, using whitespace, to define scope; such
as the scope of loops, functions and classes. Other programming
languages often use curly-brackets for this purpose.

Compare between C++ & Python
C++
#include <iostream>
using namespace std;
int main ()
{
int x,y,z;
cin >> x >> y;
z=x+y;
cout << z;
Return0;
} output : value z
Python
x=2
y=3
print(x+y)
output :5
5

Chapter One
Python syntax and Python Variables
6

Python syntax
Writing the first line in Python
print("coding academy!")
_______________________________________________
What is output :
print("Hello, World!")
Output : ------------------
print (“jouda”)
Output : ------------------
print ("23")
Output : ------------------

Python - Variables
• variables are containers for storing data values.
• Creating Variables:
Python has no command for declaring a variable.
A variable is created the moment you first assign a value to it.
x = 27
y = "jouda"
print(x)
print(y)
Variables do not need to be declared with any particular type,
and can even change type after they have been set.
x = 4 # x is of type int
x = "Sally" # x is now of type str
print(x)

Python - Variables Cont.
• Casting
If you want to specify the data type of a variable, this can be done with casting.
x = str(3) # x will be '3'
y = int(3) # y will be 3
z = float(3) # z will be 3.0
• Get the Type
You can get the data type of a variable with the type() function:
x = 5
y = "John"
print(type(x))
print(type(y))

Python - Variables Cont.
Single or Double Quotes?
String variables can be declared either by using single or
double quotes:
x = "Jouda"
# is the same as
x = 'Jouda'
Case-Sensitive
a = 4
A = "Sally"
#A will not overwrite a

Python - Variable Names
Variable Names:
• A variable can have a short name (like x and y) or a more descriptive
name (age, carname, total_volume).
• Rules for Python variables:A variable name must start with a letter or
the underscore character.
• A variable name can not start with a number.
• Variable names are case-sensitive (age, Age and AGE are three
different variables).

Python - Variable Names Cont.
Example
Legal variable names:
myvar = "Jouda"
my_var = "Jouda"
_my_var = "Jouda"
myVar = "Jouda"
MYVAR = "Jouda"
myvar2 = "Jouda"
Example
Illegal variable names:
2myvar = "Jouda"
my-var = "Jouda"
my var = "Jouda"

Multi Words Variable Names
• Variable names with more than one word can be difficult to read.
MyVariableName = "Jouda"
myVariableName = "Jouda"
my_variable_name = "Jouda"

Python Variables - Assign Multiple Values
1- x, y, z = "Ahmed", "Ali", "Mohamed"
print(x)
print(y)
print(z)
2- x = y = z = "Orange"
print(x)
print(y)
print(z)

Python - Output Variables
Output Variables:
The Python print() function is often used to output variables.
x = "jouda mohamed"
print(x)
Output : jouda mohamed
x = "Jouda"
y = "Mohamed"
z = "Qamar"
print(x, y, z)
Output : Jouda Mohamed Qamar
x = "Jouda"
y = "Mohamed"
z = "Qamar"
print(x + y + z)
Output : Jouda Mohamed Qamar
x = 5
y = 10
print(x + y)
Output : 15

Simple Questions
A- using python writing the programs :
1- Create a variable named carname and assign the value lada to it.
2- Create a variable named x and assign the value 200.5 to it.
3- Display the sum of 200 + 1000, using two variables: x and y.
4- Create a variable called z, assign x + y to it, and display the result.
B- What is error correction:
I. 2my-first_name = "mohamed"
II. x="2”
y= 3.5
print (“x+y")

Summary
• Anything inside double quotation marks is printed as is.
• Print () To output text, a number, or anything I want.
• Creating variables and knowing how to create more than one value
inside a variable, as well as the rules for creating variables.
• Knowing the types of variables and how to change between them and
doing Costing.
• Determine the type of the variable through the command type().

Chapter Two
Python Data Types and Python Operators and input
19

Python Data Types
In programming, data type is an
important concept.
Variables can store data of
different types, and different types
can do different things.
Text str
Numeric int, float, complex
Sequence list, tuple, range
Mapping dict
Set set, frozenset
Boolean bool
Binary bytes, bytearray, memoryview
None NoneType

Python Numeric Data type.
In Python, numeric data type is used to hold numeric values.
Integers, floating-point numbers and complex numbers fall under Python numbers category.
They are defined as int, float and complex classes in Python.
int - holds signed integers of non-limited length.
float - holds floating decimal points and it's accurate up to 15 decimal places.
complex - holds complex numbers.
We can use the type() function to know which class a variable or a value belongs to.

Example
num1 = 5
print(num1, 'is of type', type(num1))
num2 = 2.0
num3 = 1+2j
Output
5 is of type <class 'int'>
2.0 is of type <class 'float'>
(1+2j) is of type <class 'complex'>

Python List Data Type.
List is an ordered collection of similar or different types of items separated by commas and
enclosed within brackets [ ].
For example
languages = ["c++", "R", "Python"]
Access List Items
To access items from a list, we use the index
number (0, 1, 2 ...)
languages = ["c++", “R", "Python"]
# access element at index 0
print(languages[0]) # Swift
print(languages[2]) # Python

Python Tuple Data Type
• Tuple is an ordered sequence of items same as a list.
• The only difference is that tuples are immutable.
• Tuples once created cannot be modified.
product = ('Xbox', 499.99)
Access Tuple Items
# create a tuple
product = ('Microsoft', 'Xbox', 499.99)
print(product[0]) # Microsoft
print(product[1]) # Xbox

Python String Data Type
String is a sequence of characters represented by either single or double quotes.
For example
name = 'Python'
print(name)
message = 'Python for beginners'
print(message)
Output
Python
Python for beginners

Python Set Data Type
Set is an unordered collection of unique items. Set is defined by values separated by
commas inside braces { }
# create a set named student_id
student_id = {112, 114, 116, 118, 115}
# display student_id elements
print(student_id)
# display type of student_id
print(type(student_id))
Output
{112, 114, 115, 116, 118}
<class 'set'>

Python Booleans
Booleans represent one of two values: True or False.
Boolean Values
• In programming you often need to know if an expression is True or False.
• You can evaluate any expression in Python, and get one of two answers, True or False.
print(10 > 9)
print(10 == 9)
print(10 < 9)

Python Operators
Operators are used to perform operations on variables and values.
Operator Name Example
+ Addition x + y
- Subtraction x - y
* Multiplication x * y
/ Division x / y
% Modulus x % y
** Exponentiation x ** y
// Floor division x // y

Type Conversion
x = 1 # int
y = 2.8 # float
z = 1j # complex
#convert from int to float:
a = float(x)
#convert from float to int:
b = int(y)
#convert from int to complex:
c = complex(x)
print(a)
print(b)
print(c)
print(type(a))
print(type(b))
print(type(c))

Python Casting
- Specify a Variable Type
• There may be times when you want to specify a type on to a variable. This can be
done with casting. Python is an object-orientated language, and as such it uses
classes to define data types, including its primitive types.
• Casting in python is therefore done using constructor functions:
• int() - constructs an integer number from an integer literal, a float literal (by
removing all decimals), or a string literal (providing the string represents a whole
number)
• float() - constructs a float number from an integer literal, a float literal or a string
literal (providing the string represents a float or an integer)
• str() - constructs a string from a wide variety of data types, including strings,
integer literals and float literals

#int
x = int(1) # x will be 1
y = int(2.8) # y will be 2
z = int("3") # z will be 3
#float
x = float(1) # x will be 1.0
y = float(2.8) # y will be 2.8
z = float("3") # z will be 3.0
w = float("4.2") # w will be 4.2
#string
x = str("s1") # x will be 's1'
y = str(2) # y will be '2'
z = str(3.0) # z will be '3.0'

input in Python

input in Python
input (): This function first takes the input from the user and converts it
into a string.
val = input("Enter your value: ")
print(val)
# Python program showing
# a use of input()

Simple program using input,define to var.
name and input for your name by n.
name = input('What is your name?n')
# n ---> newline ---> It causes a line break
print(name)

input in Python cont.
Note: input() function takes all the input as a string only.
• There are various function that are used to take as desired input few
of them are :
int(input())
float(input())

Multiple inputs from user in Python
• using split() method :
This function helps in getting multiple inputs from users. It breaks the
given input by the specified separator. If a separator is not provided
then any white space is a separator. Generally, users use a split()
method to split a Python string but one can use it in taking multiple
inputs.
Syntax :
input().split(separator, maxsplit)

Multiple inputs from user in Python
# taking two inputs at a time
x, y = input("Enter two values: ").split()
print("Number of boys: ", x)
print("Number of girls: ", y)
print()
# taking three inputs at a time
x, y, z = input("Enter three values: ").split()
print("Total number of students: ", x)
print("Number of boys is : ", y)
print("Number of girls is : ", z)
print()

Programs by python
• using Python, create a simple program to calculate the sum of two
numbers.

Programs by python
• using Python, create a simple program to calculate area of rectangle
height = float (input ("Enter Height :"))
width = float (input ("Enter width :"))
print ("The result is :",height*width)

Programs by python
• If the computer
programming course
has a final score of
100, please create a
program to read the
students’name and
code, and then know
the grade of each
student.
student_name = str (input ("Enter Student Name : "))
student_id = int (input ("Enter Student id : "))
degree = float (input ("Enter Student degree : "))
if degree >= 80 :
print ("A")
elif degree >= 70 :
print ("B")
elif degree >= 60 :
print ("C")
elif degree >= 50 :
print ("D")
else :
print ("F")

Chapter Three
Python Conditions and If statements and
LOOPs (Control Flow in Python).

Python If ... Else
Python supports the usual logical conditions from mathematics:
• Equals: a == b
• Not Equals: a != b
• Less than: a < b
• Less than or equal to: a <= b
• Greater than: a > b
• Greater than or equal to: a >= b
These conditions can be used in several ways, most commonly in "if statements" and loops.

if condition: statement1 statement2 # Here if the condition is true, if block # will consider only statement1 to be inside # its block.
if condition:
statement1
statement2
# Here if the condition is true, if block
# will consider only statement1 to be inside
# its block.
Flowchart of Python if statement

Example: Python if Statement
# python program to illustrate If statement
i = 10
if (i > 15):
print("10 is less than 15")
print("I am Not in if")
Output:
I am Not in if

if-else
Syntax:
if (condition):
# Executes this block if
# condition is true
else:
# Executes this block if
# condition is false
FlowChart of Python if-else statement

Example : Python if-else statement
# python program to illustrate If else statement
i = 20
if (i < 15):
print("i is smaller than 15")
print("i'm in if Block")
else:
print("i is greater than 15")
print("i'm in else Block")
print("i'm not in if and not in else Block")
Output:
i is greater than 15
i'm in else Block
i'm not in if and not in else Block

if-elif-else ladder
Syntax:
if (condition):
statement
elif (condition):
statement
.
.
else:
statement
FlowChart of Python if else elif statements

Example: Python if else elif statements
# Python program to illustrate if-elif-else ladder
i = 20
if (i == 10):
print("i is 10")
elif (i == 15):
print("i is 15")
elif (i == 20):
print("i is 20")
else:
print("i is not present")
Output: i is 20

Chaining comparison operators in Python
">" | "<" | "==" | ">=" | "<=" | "!=" | "is" ["not"] | ["not"] "in"
Chaining in Comparison Operators:
1.Comparisons yield boolean values: True or False.
2.Comparisons can be chained arbitrarily.
For example:
# Python code to illustrate
# chaining comparison operators
x = 5
print(1 < x < 10)
print(10 < x < 20 )
print(x < 10 < x*10 < 100)
print(10 > x <= 9)
print(5 == x > 4)
Output
True
False
True
True
True
Another Example:
# Python code to illustrate
# chaining comparison operators
a, b, c, d, e, f = 0, 5, 12, 0, 15, 15
exp1 = a <= b < c > d is not e is f
exp2 = a is d > f is not c
print(exp1)
print(exp2)
Output
True
False

And
a = 200
b = 33
c = 500
if a > b and c > a:
print("Both conditions are True")
a > b and c > a

Or
a = 200
b = 33
c = 500
if a > b or a > c:
print("At least one of the conditions is True")
a > b or a > c

Not
a = 33
b = 200
if not a > b:
print("a is NOT greater than b")
not a > b

For Loops

Python For Loops
For Loops Syntax
for var in iterable:
# statements
Flowchart of for loop

Examples of For Loops in Python
• Example 1: Using For Loops in Python List:
# Python program to illustrate
# Iterating over a list
l = ["coding", "academy", "for programming"]
for i in l:
print(i)
Output :
coding
academy
for programming

Continue Statement in Python
# Prints all letters except 'e' and 's'
for letter in 'geeksforgeeks':
if letter == 'e' or letter == 's':
continue
print('Current Letter :', letter)
Output:
Current Letter : g
Current Letter : k
Current Letter : f
Current Letter : o
Current Letter : r
Current Letter : g
Current Letter : k

Break Statement in Python
# break the loop as soon it sees 'e'
# or 's'
if letter == 'e' or letter == 's':
break
print('Current Letter :', letter)
Output:
Current Letter : e

Pass Statement in Python
# An empty loop
pass
print('Last Letter :', letter)
Output: Last Letter : s

range () function in Python
# Python Program to
# show range() basics
# printing a number
for i in range(10):
print(i, end=" ")
# performing sum of first 10 numbers
sum = 0
for i in range(1, 10):
sum = sum + i
print("nSum of first 10 numbers :", sum)
Output:
0 1 2 3 4 5 6 7 8 9
Sum of first 10 numbers : 45

For loop in Python with else
# for-else loop
for i in range(1, 4):
print(i)
else: # Executed because no break in for
print("No Breakn")
Output:
1
2
3
No Break

Python While Loop

While Loop
# while loop
count = 0
while (count < 3):
count = count + 1
print("Hello Geek")
Output
Hello Geek
Hello Geek
Hello Geek

While Loop
# Single statement while block
count = 0
while (count < 5): count += 1; print("Hello Geek")
Output:
Hello Geek
Hello Geek
Hello Geek
Hello Geek
Hello Geek

The else Statement
With the else statement we can run a block of code once when the
condition no longer is true:
i = 1
while i < 6:
print(i)
i += 1
else:
print("i is no longer less than 6")

Simple Questions
What is output :
1. p, q, r = 10, 20 ,30
print(p, q, r)
2.
a = 3
b = 5
if a>b : print ("TRUE")
else : print ("False")

Simple Questions
3.
a = 50
b = 10
if a>b:
print("Hello World")
Write a program python :
1. Print "Yes" if a is equal to b, otherwise print "No".
2. Print "1" if a is equal to b, print "2" if a is greater than b, otherwise
print "3".
3. Print "Hello" if a is equal to b, or if c is equal to d.

Simple Questions
The format function, when applied on a string returns :
- List - int - bool - str
What is output:

Chapter four
Python Arrays and function.

Python Arrays

an array is a collection of items stored at contiguous memory locations.
The idea is to store multiple items of the same type together.
Python Arrays

Creating a Array
Array in Python can be created by importing array module.
array(data_type, value_list)
is used to create an array with data type and value list specified in its
arguments.

# Python program to demonstrate
# Creation of Array
# importing "array" for array creations
import array as arr
# creating an array with integer type
a = arr.array('i', [1, 2, 3])
# printing original array
print ("The new created array is : ", end =" ")
for i in range (0, 3):
print (a[i], end =" ")
print()
# creating an array with double type
b = arr.array('d', [2.5, 3.2, 3.3])
# printing original array
print ("The new created array is : ", end =" ")
for i in range (0, 3):
print (b[i], end =" ")
The new created array is : 1 2 3
The new created array is : 2.5 3.2 3.3

Array & List Methods
Python has a set of built-in methods that you can use on lists/arrays.
Method Description
append() Adds an element at the end of the list
clear() Removes all the elements from the list
copy() Returns a copy of the list
count() Returns the number of elements with the specified value.
extend() Add the elements of a list (or any iterable), to the end of the current list
index() Returns the index of the first element with the specified value
insert() Adds an element at the specified position
pop() Removes the element at the specified position
remove() Removes the first item with the specified value
reverse() Reverses the order of the list
sort() Sorts the list

Python Functions

Python Functions
Functions is a block of statements that return the specific task.
Syntax: Python Functions

Creating a Python Function
We can create a Python function using the def keyword.
# A simple Python function
def fun():
print("Welcome Func ")

Calling a Python Function
After creating a function we can call it by using the name of the function
followed by parenthesis containing parameters of that particular
function.
def fun():
print("jouda")
# Driver code to call a function
fun()

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