Introduction to Python Unit -1 Part .pdf

Python is an interpreted, object-oriented, high-level programming
language with dynamic semantics developed by Guido van
Rossum. It was originally released in 1991.
Python Use Cases
•Creating web applications on a server
•Building workflows that can be used in conjunction with software
•Connecting to database systems
•Reading and modifying files
•Performing complex mathematics
•Processing big data
•Developing production-ready software
INTRODUCTION TO PYTHON

Popularity of Programming Language Index:

Difference between Compiler and Interpreter
COMPILER INTERPRETER
A compiler takes the entire
program in one go.
An interpreter takes the single
line of code at a time.
A compiler generates an
intermediate machine code.
An interpreter never produces
any intermediate code.
Error are displayed after entire
program is checked. (If any)
Errors are displayed for every
instruction is interpreted. (If
any)
Memory requirements is more. Memory requirement is less.
Examples: C, C++,C#, Java etc. Examples: BASIC, Python, Perl,
Ruby etc.

Some important reasons for popularity:
•Easy to read and Code: Python is a very high-level programming language,
yet it is effortless to learn and learning the basic Python syntax is very easy,
as compared to other popular languages like C, C++, and Java.
•Free and Open source: Python is developed under an OSI-approved open
source license. Hence, it is completely free to use, even for commercial
purposes.
•Robust standard Library: This means that programmers don’t have to write
their code for every single thing unlike other programming languages.
•Interpreted language: When a programming language is interpreted, it
means that the source code is executed line by line, and not all at once.
There is no need to compile Python because it is processed at runtime by
the interpreter.
•Portable: Python is portable in the sense that the same code can be used
on different machines.
•Object-Oriented and Procedure-Oriented: One of the critical Python
features is that it supports both object-oriented and procedure-oriented
programming.

Python History and Versions
•Python laid its foundation in the late 1980s.
•The implementation of Python was started in December 1989 by Guido Van Rossum at
CWI in Netherland.
•In February 1991, Guido Van Rossum published the code (labeled version 0.9.0) to
alt.sources.
•In January1994, Python 1.0 was released with new features like lambda, map, filter, and
reduce.
•In October 2000, Python 2.0 added new features such as list comprehensions, garbage
collection systems.
•On December 2008, Python 3.0 (also called "Py3K") was released. It was designed to
rectify the fundamental flaw of the language.
•ABC programming language is said to be the predecessor of Python language, which was
capable of Exception Handling and interfacing with the Amoeba Operating System.
•Latest version of Python is 3.11.3

IDE (Integrated Development Environment Software)
An integrated development environment (IDE) is a software
application that helps programmers develop software
code efficiently. It increases developer productivity by
combining capabilities such as software editing, building,
testing, and packaging in an easy-to-use application.

Programming Cycle:
1. Python’s programming cycle is dramatically shorter
than that of traditional programming cycle.
2. In Python, there are no compile or link steps.
3. Python programs simply import modules at runtime
and use the objects they contain. Because of this, Python
programs run immediately after changes are made.
4. In cases where dynamic module reloading can be
used, it is even possible to change and reload parts of a
running program without stopping it at all.

Programming Cycle (Cont...):
5. Python’s impact on the programming cycle is as
follows:

Traditional Programming Cycle Python Programming Cycle
The programmer writes the code,
compiles it, and executes it.
The programmer writes the code and
then runs it.
The code is compiled into an
executable file.
The code is directly interpreted by the
Python interpreter.
The programmer must declare
variables before using them.
The programmer does not need to
declare variables before using them.
The programmer needs to specify the
data type of the variables.
The programmer does not need to
specify the data type of the variables.
The programmer needs to free the
memory allocated for the variables.
The interpreter automatically releases
the memory allocated for the
variables.
The programmer needs to handle
memory management.
The interpreter handles memory
management.

Q: What makes python programming different from
others?
Ans. Python programming is different from other languages in a
few key ways.
Interpreted language
Python is an interpreted language, meaning that your code is not
compiled into an executable program. Instead, the Python
interpreter runs your code line by line, translating each line into
machine code.
Dynamically type
Python is a dynamically typed language, which means that you
don’t have to declare the types of your variables ahead of time.
High-level language
Python is a very high-level language, which means that it abstracts
away a lot of the low-level details that you would have to deal with
in other languages.

Python script:
A Python script, the file containing the commands, is
structured to be executed like a program. These files are
designed to contain various functions and import various
modules. Python interactive shell or the respective
command line is used to execute the script, to perform a
specific task.
Script:
•It is a plain text file containing Python code.
•It has the extension .py
•It can be executed directly.
•Python interpreter is responsible for executing the
Python scripts.

Different ways to run python script:
•Interactive mode
•Command Line
•Text Editor
•IDE

•Interactive mode
This is the most frequently used way to run a Python code. Here basically we do
the following:
1. Open command prompt / terminal in your system
2. Enter the command - python or python3 (based on python version installed in
your system)
3. If we see these : >>> then, we are into our python prompt. It will look
something like this:

•Command Line
Follow the below steps to run a Python Code through command line -
1.Write your Python code into any text editor.
2.Save it with the extension .py into a suitable directory
3.Open the terminal or command prompt.
4.Type python/python3 (based on installation) followed by the file name.py –
python filename.py

•Run Python on Text Editor
If you want to run your Python code into a text editor -- suppose
VS Code, then follow the below steps:
1.From extensions section, find and install 'Python' extension.
2.Restart your VS code to make sure the extension is installed
properly.
3.Create a new file, type your Python code and save it.
4.Run it using the VS code's terminal by typing the command "py
hello.py“
5.Or, Right Click -> Run Python file in terminal

•Run Python on IDLE(IDE)
Python installation comes with an Integrated Development and
Learning Environment, which is popularly known as IDLE.
Steps to run a python program on IDLE:
1.Open the Python IDLE(navigate to the path where Python is
installed, open IDLE(python version))
2.The shell is the default mode of operation for Python IDLE. So,
the first thing you will see is the Python Shell –
3.You can write any code here and press enter to execute
4.To run a Python script you can go to File -> New File
5.Now, write your code and save the file –
6.Once saved, you can run your code from Run -> Run
Module Or simply by pressing F5 --

Execute Python Syntax
As we learned in the previous page, Python syntax
can be executed by writing directly in the
Command Line:
>>> print("Hello, World!")
Hello, World!
Or by creating a python file on the server, using the
.py file extension, and running it in the Command
Line:
C:UsersYour Name>python myfile.py
Python Syntax

Python Indentations
Where in other programming languages the
indentation in code is for readability only, in Python
the indentation is very important.
Python uses indentation to indicate a block of code.
Example:-
Python will give you an error if you skip the
indentation:
Example
Python Syntax
if 5 > 2:
print("Five is greater than two!")
if 5 > 2:
print("Five is greater than two!")

Comments can be used to explain Python code.
Comments can be used to make the code more
readable.
Comments can be used to prevent execution when
testing code.
Creating a Comment
Comments starts with a #, and Python will ignore them:
Example
#This is a comment
print("Hello, World!")
Comments can be placed at the end of a line, and Python
will ignore the rest of the line:
Example
print("Hello, World!") #This is a comment
Python Comment

Multi Line Comments
Python does not really have a syntax for multi line
comments.
To add a multiline comment you could insert a # for each
line:
Example
#This is a comment
#written in
#more than just one line
Or, not quite as intended, you can use a multiline string.
Python Comment

Multi Line Comments
Since Python will ignore string literals that are not assigned to a
variable, you can add a multiline string (triple quotes) in your code,
and place you comment inside it:
Example
"""
This is a comment
written in
more than just one line
"""
As long as the string is not assigned to a variable, Python will read the
code, but then ignore it, and you have made a multiline comment.
Python Comment

User Input:
•Python allows for user input.
•That means we are able to ask the user for input.
•The method is a bit different in Python 3.X than Python 2.7.
•Python 3.6 uses the input() method.
•Python 2.7 uses the raw_input() method.
Python 3.6
username = input("Enter username:")
print("Username is: " + username)
Python 2.7
username = raw_input("Enter username:")
print("Username is: " + username)
Python USER INPUT

Creating Variables
Variables are containers for storing data values.
Unlike other programming languages, Python has no
command for declaring a variable.
A variable is created the moment you first assign a
value to it.
Example
x = 5
y = "John"
print(x)
print(y)
Python Variables

Variables do not need to be declared with any
particular type and can even change type after they
have been set.
Example
x = 4 # x is of type int
x = "Sally" # x is now of type str
print(x)
String variables can be declared either by using single
or double quotes:
Example
x = "John"
# is the same as
x = 'John'
Python Variables

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 cannot start with a number
A variable name can only contain alpha-numeric
characters and underscores (A-z, 0-9, and _ )
Variable names are case-sensitive (age, Age and AGE
are three different variables)
*Remember that variable names are case-sensitive
Python Variables

Assign Value to Multiple Variables
Python allows you to assign values to multiple variables in one line:
Example
x, y, z = "Orange", "Banana", "Cherry"
print(x)
print(y)
print(z)
And you can assign the same value to multiple variables in one
line:
Example
x = y = z = "Orange"
print(x)
print(y)
print(z)
Python Variables

Output Variables
The Python print statement is often used to output variables.
To combine both text and a variable, Python uses the +
character:
Example
x = "awesome"
print("Python is " + x)
You can also use the + character to add a variable to another
variable:
Example
x = "Python is "
y = "awesome"
z = x + y
print(z)
Python Variables

Output Variables
For numbers, the + character works as a mathematical
operator:
Example
x = 5
y = 10
print(x + y)
If you try to combine a string and a number, Python will give
you an error:
Example
x = 5
y = "John"
print(x + y)
Python Variables

There are three numeric types in Python:
int
float
complex
Variables of numeric types are created when you assign a value to
them:
Example
x = 1 # int
y = 2.8 # float
z = 1+1j # complex
To verify the type of any object in Python, use the type() function:
Example
print(type(x))
print(type(y))
print(type(z))
Python Numbers

Int
Int, or integer, is a whole number, positive or negative,
without decimals, of unlimited length.
Example
Integers:
x ,y, z = 1, 35656222554887711, 54646543
print(x)
print(y)
print(z)
Python Numbers

Float
Float, or "floating point number" is a number, positive
or negative, containing one or more decimals.
Example
Floats:
x ,y, z = 1.0, 1.015, -0.25
print(x)
print(y)
print(z)
Python Numbers

Float can also be scientific numbers with an "e" to
indicate the power of 10.
Example
Floats:
x , y ,z= 35e3, 12E4, -87.7e100
print(x)
print(y)
print(z)
Python Numbers

Complex
Complex numbers are written with a "j" as the
imaginary part:
Example
Complex:
x, y, z = 3+5j, 5j, -5j
print(x)
print(y)
print(z)
Python Numbers

Type Conversion
You can convert from one type to another with the int(), float(),
and complex() methods:
Example
Convert from one type to another:
x = 1 # int y = 2.8 # float z = 1j # complex
a = float(x) #convert from int to float
b = int(y) #convert from float to int
c = complex(x) #convert from int to complex
print(a)
print(b)
print(c)
print(type(a))
print(type(b))
print(type(c))
Note: You cannot convert complex numbers into another number type.
Python Numbers

Random Number
Python does not have a random() function to make a
random number, but Python has a built-in module
called random that can be used to make random
numbers:
Example
Import the random module, and display a random
number between 1 and 9:
import random
print(random.randrange(1,10))
Python Numbers

Reserved Words (Keywords):
Keywords in Python are reserved words that can not be used as a
variable name, function name, or any other identifier.
Python Numbers

A combination of operands and operators is called
an expression. The expression in Python produces some value or
result after being interpreted by the Python interpreter.
Ex:
x = 25 # a statement
x = x + 10 # an expression
print(x)
•An expression in Python can
contain identifiers, operators, and operands.
•An identifier is a name that is used to define and
identify a class, variable, or function in Python.
•An operand is an object that is operated on.
•An operator is a special symbol that performs the
arithmetic or logical computations on the operands.
Python Expression

Types of Expression
There are various types of expression:
•Constant Expressions: A constant expression in Python that contains only constant
values is known as a constant expression.
x = 10 + 15
print("The value of x is: ", x)
•Arithmetic Expressions: An arithmetic expression is a combination of numeric
values, operators, and sometimes parenthesis. The result of this type of expression is
also a numeric value.
x = 10 y = 5
addition = x + y
•Integral Expressions: These are the kind of expressions that produce only integer
results after all computations and type conversions.
x = 10 y = 5.0
result = x + int(y)
Python Expression

Types of Expression (Cont...)
•Floating Expressions: These are the kind of expressions which
produce floating point numbers as result after all computations and
type conversions.
x = 10 y = 5.0
result = float(x) + y
•Relational Expressions: A relational expression in Python can be
considered as a combination of two or more arithmetic expressions
joined using relational operators. We have four types of relational
operators in Python. (>, <, >=, <=).
x=10 y=5
result= x>y
•Logical Expressions: As the name suggests, a logical expression
performs the logical computation, and the overall expression results in
either True or False (boolean result).
Python Expression

Types of Expression (Cont..)
•Bitwise Expressions: The expression in which the operation or
computation is performed at the bit level is known as a bitwise
expression in Python.
x = 25
left_shift = x << 1
right_shift = x >> 1
•Combinational Expressions: A combination expression can contain
a single or multiple expressions which result in an integer or boolean
value depending upon the expressions involved.
x = 25 y = 35
result = x + (y << 1)
Python Expression

We use Python assignment statements to assign objects to names. The
target of an assignment statement is written on the left side of the
equal sign (=), and the object on the right can be an arbitrary
expression that computes an object.
There are some important properties of assignment in Python :-
•Assignment creates object references instead of copying the objects.
•Python creates a variable name the first time when they are assigned a
value.
•Names must be assigned before being referenced.
•There are some operations that perform assignments implicitly.
Python Assignment statements

Different forms of assignment statements:
Basic form:
st = ‘abc'
print(st)
Tuple assignment:
x, y = 50, 100
print('x = ', x)
print('y = ', y)
List assignment:
[x, y] = [2, 4]
print('x = ', x)
print('y = ', y)

Different forms of assignment statements:
Sequence assignment:
a, b, c = 7,5,9
print('a = ', a)
print('b = ', b)
print('c = ', c)
Multiple- target assignment:
x = y = 75
print(x, y)
Augmented assignment :
x = 2
x += 1 # equivalent to: x = x + 1
print(x)

Python divides the operators in the following
groups:
•Arithmetic operators
•Assignment operators
•Comparison operators
•Logical operators
•Identity operators
•Membership operators
•Bitwise operators
Python Operators

Python Operators (Arithmetic)
Operator Name Example
+ Addition x + y
- Subtraction x - y
* Multiplication x * y
/ Division x / y
(Result in float)
% Modulus x % y
** Exponentiation x ** y
// Floor division x // y

Python Operators (Assignment)
Operator Example Same As
= x = 5 x = 5
+= x += 3 x = x + 3
-= x -= 3 x = x - 3
*= x *= 3 x = x * 3
/= x /= 3 x = x / 3
%= x %= 3 x = x % 3
//= x //= 3 x = x // 3
**= x **= 3 x = x ** 3

Python Operators (Comparison)
Operator Name Example
== Equal x == y
!= Not equal x != y
> Greater than x > y
< Less than x < y
>= Greater than or
equal to
x >= y
<= Less than or
equal to
x <= y

Python Operators (Logical)
Operator Description Example
and Returns True if both
statements are true
x < 5 and x < 10
or Returns True if one of the
statements is true
x < 5 or x < 4
not Reverse the result, returns
False if the result is true
not(x < 5 and x < 10)

Python Operators (Identity)
Operator Description Example
is Returns True if both variables
are the same object
x is y
is not Returns True if both variables
are not the same object
x is not y
Identity operators are used to compare the objects, not if they are equal, but
if they are actually the same object, with the same memory location:

PROGRAMS:
PROGRAMS 1: WAP to find the type of variable.
a=5
b="hello"
c=1.2
d=1+5j
print("The type of a is : ",type(a))
print("The type of b is : ",type(b))
print("The type of c is : ",type(c))
print("The type of d is : ",type(d))
OUTPUT

PROGRAMS:
PROGRAMS 2: WAP to find the square root of a number.
print("Enter the number for square root:: ")
num=float(input())
sqrt=num**0.5
print("The square root of the number is : ",sqrt)
OUTPUT

Introduction to Python Unit -1 Part .pdf

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