This document provides an introduction to the Python programming language. It discusses what Python is, why it should be used, and some key features like variables, data types, operators, conditional statements, loops, lists, tuples, modules and more. Examples are provided to demonstrate how each concept works in Python code. Links to Colab notebooks with additional Python examples and exercises are included at the end.

1. Introduction to Python
Amrita A Nair & Nandu Sankar
S5 AE
A session by GDSC CET

2. What is Python?
A Programming Language :)
● Interpreted
● Object-oriented
● Dynamic semantics
● High-level built in data structures

3. ● Modules and packages
● Program modularity
● Code reuse
● Easy-to-use
● Easy debugging
Why use Python?

4. The ‘Hello World'
The first program by
every programmer ever:

5. print("Hello World")

6. • A variable is a name given to a memory location. It is the basic unit of
storage in a program.
• The value stored in a variable can be changed during program
execution.
Variables

7. ● A variable name must start with a letter or the underscore character.
● A variable name cannot start with a number. Eg: 1str, 94name
● A variable name can only contain alphanumeric characters and
underscores (A-z, 0-9, and _ ).
● Variable names are case-sensitive (name, Name and NAME are three
different variables).
● The reserved words (keywords) cannot be used naming the variable.
Rules for creating variables

8. Reserved keywords

9. name = “Michael”
age = 34
salary = 1374.5
print(name)
print(age)
print(salary)

10. Comments
● Comments in Python are the lines in the code that are ignored by the
compiler during the execution of the program.
● Comments enhance the readability of the code and help the
programmers to understand the code.
● They are of 2 types :
○ Single line comments
○ Multiline comments

11. #This is an example of a single line comment
‘‘‘This is an example of a
multiline comment’’’

12. • Developers often have a need to interact with users, either to get data
or to provide some sort of result.
• In order to get input from the user, we use the input() function built-in
with Python.
• This function first takes the input from the user and then evaluates the
expression while Python automatically identifies the datatype. If the
input provided is not correct then either a syntax error or an exception
is raised by Python.
Receiving Input

13. val = input(“Enter a value : “)
print(val)

14. To know the type of data that a variable is storing, we use the type()
function.
Type of input

15. val = input(“Enter a value : “)
print ("Type of data", type(val))

16. Type Conversion
● Whatever you enter as input, the input() function converts it into a string.
● If you enter an integer value, input() function converts it into a string.
● You need to explicitly convert it into an integer in your code using what is
called typecasting.

17. #No conversion
val = input("Enter a value : ")
print("Type of data", type(val))
#Integer Conversion
int_val = int(val)
print("Type of data", type(int_val))
#OR
val = int(input("Enter a value : "))
print("Type of data", type(val))

18. ● Strings are arrays of bytes representing Unicode characters.
Eg: “My name is Jim”
● Square brackets can be used to access elements of the string.
Strings

19. ● Strings in Python can be created using single quotes, double quotes or
even triple quotes.
Strings

20. Str1 = “College of Engineering Trivandrum”
print(Str1[0])

21. Inbuilt string functions

22. Inbuilt string functions

23. Operators & Operator Precedence
Arithmetic operators: + - * / % // **
Assignment operators: =, +=, -=, *=, /=
Comparison operators: ==, >, <, >=, <=, !=
Logical operators: and, or, not
Identity operators: is, is not
Membership operators: in, not in

24. BODMAS/PEMDAS

25. print(1 + 5)
print(10*'hello ')
print(6<1)

26. If, Elif & Else Statements
● Conditional Statements
● Used for Decision Making
● Control Flow Statement
Note: Indent!!! In python, indents are used to indicate that a piece of code
belongs to a certain block, i.e, the code that is at the same level of
indentation is considered a block of code.

27. If Statement
● Used for Decision Making
Syntax:
if <condition>:
statement(s)

28. If Statement

29. a = 1
b = 1
if a == b:
print("A & B are equal!")

30. Else Statement
● Used to specify what to do when the condition in if returns ‘false’.
Syntax:
if <conditions>:
ifstatements
else:
elsestatements

31. Else Statement

32. a = 1
b = 2
if (a == b):
print("A & B are equal!")
else:
print("A and B are not equal :(")

33. If- Elif- Else Statement
● Used when the multiple case are required.
● Next elif condition checked only if the previous if (or elif) condition is false.
● Cannot use elif without an if block prior to it

34. If- Elif- Else Statements
Syntax:
if <condition-1>:
ifstatements
elif <condition-2>:
ifstatements
elif <condition-n>:
ifstatements
Else:
elsestatements

35. If- Elif- Else Statement

36. a = 1
b = 2
if a == b:
print("A & B are equal!")
elif a > b:
print("A is greater than B :)")
else:
print("A and B are not equal :(")

37. While Loop
● Used to perform a set of instructions repeatedly until a specific condition
is satisfied
● Entry controlled loop (condition is checked before the statements are
executed)
Syntax:
while < condition>:
statements

38. n = 1
while n<=5:
print('Python is fun!')
n+=1

39. • Most widely used data types in Python.
• Square brackets [ ], comma separated.
• Data items of any data type, be it an integer type or a boolean type.
• Mutable, i.e, list can be edited.
Lists

40. List1 = [10, 'ABC', 13.5435, True]
print(List1)
List1 = [10, 20, 14]
print(List1)
List = ["My", "Name", "is", "Amrita"]
print(List[0])
List = [['GDSC', 'CET'] , ['Google Developer Student Club']]
print(List)

41. List1 = ['a','b','c','d','e']
print(List1)
List2 = List1[:-4]
print(List2)
List3 = List1[-4:-1]
print(List3)
Sliced_List = List[::-1]
print(Sliced_List)
List1 = []
print(len(List1))

42. L1 = [1,2,3,4,5,6,7,8,9,0]
print(len(L1))
L1.pop()
print(L1)
L1.pop(2)
print(L1)
L1.remove(5)
L1.remove(6)
print(L1)
L1.extend(['a', 4, 4.45])
print(L1)

43. For Loop
● Entry Controlled Loop
Syntax:
for <condition> :
Statements

44. for i in range(0,10):
print('Python is fun!')
for i in range(0,2):
for j in range (0,2):
print('Python is so fun!')#nested loop, prints 2*2 times

45. • Parenthesis(), comma separated.
• Data items of any data type, be it an integer type or
a boolean type.
• Immutable, i.e, tuples cannot be edited once
stored, only deleted.
Tuples

46. tup1 = ('a', 'b', 1, 2, 3);
tup2 = (12, 34.56);
print(tup1)
print(tup2)
print(tup2[0])
print(tup1[1:5])
#del tup1
#print (tup1)
tup2 = (12, 34.56);
tup3 = tup1 + tup2;
print (tup3)

47. ● Import modules and libraries to access functions
present in them
Syntax:
I. import <modulename>
II. from <modulename> import <function>
III. import <modulename> as <abbrreviation>
Importing Modules

48. import math
n= math.pi*5
print(n)
import numpy as np
n= np.array([1,2,3,43,554])
print(type(n))

49. Links to Colab Notebooks:
https://colab.research.google.com/drive/1CBT4XL8oyyWx
237lIgpDPGoHE9gUY8Zf?usp=sharing
https://colab.research.google.com/drive/1F20FdDZS6Yo7
jlGuPwD9BHs7Ri_5X02Q?usp=sharing