This document provides an introduction to Python programming. It discusses the history and origins of Python, why it is useful for programming, its core features like object-oriented programming and indentation, basic syntax like variables, data types, and keywords. It also covers strings, booleans, and how to assign values and combine text in strings.

1. COMPUTING APPLICATIONS
WITH PYTHON
UNIT - I

2. Introduction:
What is Python?
Python is an interpreted, object-oriented, high-level programming language with dynamic semantics.
History of Python:
• In the late 1980s, history was about to be written. It was that time when working on Python started. Soon
after that, Guido Van Rossum began doing its application-based work in December of 1989 at Centrum
Wiskunde & Informatica (CWI) which is situated in the Netherlands.
• It was started firstly as a hobby project because he was looking for an interesting project to keep him
occupied during Christmas.
• The programming language in which Python is said to have succeeded is ABC Programming Language,
which had interfacing with the Amoeba Operating System and had the feature of exception handling.
• The inspiration for the name came from BBC’s TV Show – ‘Monty Python’s Flying Circus’, as he was a big
fan of the TV show and also he wanted a short, unique and slightly mysterious name for his invention and
hence he named it Python!

3. • The language was finally released in 1991. When it was released, it used a lot fewer codes to
express the concepts, when we compare it with Java, C++ & C.
• Its main objective is to provide code readability and advanced developer productivity.
Why to use Python (Need for Python Programming):
The following are the primary factors to use python:
1. Python is object-oriented Structure supports such concepts as polymorphism, operation
overloading and
multiple inheritance.
2. Indentation: Indentation is one of the greatest feature in python
3. It’s free (open source) Downloading python and installing python is free and easy

4. 4. It’s Powerful
• Dynamic typing
• Built-in types and tools
• Library utilities
• Automatic memory management
5. It’s Portable
• Python runs virtually every major platform used today
• As long as you have a compactable python interpreter installed, python programs will run in exactly the same
manner, irrespective of platform.
6. It’s easy to use and learn
• No intermediate compile
• Python Programs are compiled automatically to an intermediate form called byte code, which the interpreter
then reads.
• This gives python the development speed of an interpreter without the performance loss inherent in purely
interpreted languages.
• Structure and syntax are pretty intuitive and easy to grasp.

5. 7. Interpreted Language
Python is processed at runtime by python Interpreter
8. Interactive Programming Language
Users can interact with the python interpreter directly for writing the programs
9. Straight forward syntax
The formation of python syntax is simple and straight forward which also makes it popular.

6. Variables:
• Variables are nothing but reserved memory locations to store values. This means that when you create a
variable you reserve some space in memory.
• Based on the data type of a variable, the interpreter allocates memory and decides what can be stored in the
reserved memory. Therefore, by assigning different data types to variables, you can store integers, decimals or
characters in these variables.
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)

7. Assigning Values to Variables:
Python variables do not need explicit declaration to reserve memory space. The declaration happens
automatically when you assign a value to a variable. The equal sign (=) is used to assign values to variables.
The operand to the left of the = operator is the name of the variable and the operand to the right of the =
operator is the value stored in the variable.
For example −
a= 100 # An integer assignment
b = 1000.0 # A floating point
c = "John“ # A string
print (a)
print (b)
print (c)
This produces the following result −
100
1000.0
John

8. Multiple Assignment:
Python allows you to assign a single value to several variables simultaneously.
For example :
a = b = c = 1
Here, an integer object is created with the value 1, and all three variables are assigned to the same memory
location. You can also assign multiple objects to multiple variables.
For example −
a, b, c = 1,2," MREC“
Here, two integer objects with values 1 and 2 are assigned to variables a and b respectively, and one string
object with the value "john" is assigned to the variable c.
Output Variables:
The Python print statement is often used to output variables. Variables do not need to be declared with any
particular type and can even change type after they have been set.
x = 5 # x is of type int
x = " MREC " # x is now of type str
print(x)
Output: MREC

9. • To combine both text and a variable, Python uses the “+” character:
Example:
x = "awesome"
print("Python is " + x)
Output:
Python is awesome
• You can also use the + character to add a variable to another variable:
Example:
x = "Python is "
y = "awesome"
z = x + y
print(z)
Output:
Python is awesome

10. Keywords:

11. Keyword Description
and A logical operator
as To create an alias
assert For debugging
break To break out of a loop
class To define a class
continue To continue to the next iteration of a loop
def To define a function
del To delete an object
elif Used in conditional statements, same as else if
else Used in conditional statements

12. False Boolean value, result of comparison operations
finally Used with exceptions, a block of code that will be
executed no matter if there is an exception or not
for To create a for loop
from To import specific parts of a module
global To declare a global variable
if To make a conditional statement
import To import a module
in To check if a value is present in a list, tuple, etc.
is To test if two variables are equal

13. lambda To create an anonymous function
None Represents a null value
nonlocal To declare a non-local variable
not A logical operator
or A logical operator
pass A null statement, a statement that will do nothing
raise To raise an exception
return To exit a function and return a value
True Boolean value, result of comparison operations
try To make a try...except statement
while To create a while loop
with Used to simplify exception handling
yield To end a function, returns a generator

14. Strings
Strings in python are surrounded by either single quotation marks, or double quotation marks.
'hello' is the same as "hello".
Python treats single quotes the same as double quotes.
print("Hello")
print('Hello’)
Assign String to a Variable:
Assigning a string to a variable is done with the variable name followed by an equal sign and the
string:
Example:
a = "Hello"
print(a)

15. Multiline Strings:
You can assign a multiline string to a variable by using three quotes:
a = """Lorem ipsum dolor sit a met, consectetur a dipiscing elit, sed do eiusmod tempor
in cididuntut labore et dolore magna aliqua."""
print(a)
Strings are Arrays:
Like many other popular programming languages, strings in Python are arrays of bytes
representing unicode characters.
Square brackets can be used to access elements of the string.
Example:
Get the character at position 1 (remember that the first character has the position 0):
a = "Hello, World!"
print(a[1])

16. Booleans:
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.
When you compare two values, the expression is evaluated and Python returns the Boolean
answer:
Example:
print(10 > 9)
print(10 == 9)
print(10 < 9)

17. When you run a condition in an if statement, Python returns True or False:
Example:
a = 200
b = 33
if b > a:
print("b is greater than a")
else:
print("b is not greater than a")
Output:
b is not greater than a