BASICS OF PYTHON

1. K.LEELARANI AP/CSE
KAMARAJ COLLEGE OF ENGINEERING AND TECHNOLOGY

2.  What is Python
 History of Python
 Why do people use Python
 Applications of python
 Who uses python today
 Running Python
 Variable in python
 Python Data Types
 Input() function
 Conditional and looping Statements

3.  Python is a general purpose, high level ,object
oriented programming language.
 Python is also called as Interpreted language

4.  Invented in the Netherlands, early 90s by Guido
van Rossum •
 Guido Van Rossum is fan of ‘Monty Python’s
Flying Circus’, this is a famous TV show in
Netherlands •
 Named after Monty Python •
 Open sourced from the beginning

5.  Google makes extensive use of Python in its web
search system.
 Intel, Cisco and IBM use Python for hardware
testing.
 The YouTube video sharing service is largely
written in Python
 Facebook ,instagram…

6.  Free and Open Source
 Extensible and Embeddable
 High level ,interpreted language
 Large standard libraries to solve common tasks.

7.  Web Applications
 Scientific and Numeric Computing
> Earthpy
> Astropy

8.  Simple syntax (interactive mode ,script mode)
 >>> print 'Hello world’
Hello world
>>>2+3
>>> 5

9.  A Python variable is a reserved memory location
to store values.
 In other words, a variable in a python program
gives data to the computer for processing.
 Every value in Python has a datatype.

10.  >>> year =2019
>>>type(year)
<class 'int'>
 >>> department=“CSE”
>>>type(department)
<class ‘str’>

11. Python Data Types
Numeric String List Tuple Dictionary Boolean

12.  Python has three numeric types
> integer
> floating point numbers
> Complex numbers (a+bi)
Practice:
>>>a=15
>>>type(a)
>>>b=1.5
>>>type(b)

13.  A string in python can be a series or a sequence
of alphabets, numerals and special characters.
 Single quotes or double quotes are used to
represent strings
 The first character of a string has an index 0.
Practice:
>>>department=“cse”
>>>type(department)
<class ‘str’>

14. >>> string1=“Hi Friends”
>>>string1
Concatenation Operator (+) – Combine two or
more than two strings
>>> string1 + “How are You”
Repetition Operator (*) - Repeat the same
string several times
>>> string1 *2

15.  List:
The list is a most versatile Data type available
in Python which can be written as a list of
comma-separated values (items) between square
brackets. Important thing about a list is that
items in a list need not be of the same type.
Example:
list1 = ['physics', 'chemistry', 1997, 2000];
list2 = [1, 2, 3, 4, 5 ];

16. s.no Function with description
1. cmp(list1, list2) #Compares elements of both lists
2. len(list) #Gives the total length of the list
3. max(list) # Returns item from the list with max value.
4. min(list) #Returns item from the list with min value.

17. Tuples:
A tuple is a sequence of immutable Python
objects. Tuples are sequences, just like lists. The
differences between tuples and lists are, the
tuples cannot be changed unlike lists and tuples
use parentheses, whereas lists use square
brackets.
Example:
tup1 = (1, 2, 3, 4, 5 )
tup2 = ("a", "b", "c", "d“)

18. SN Function with Description
1 cmp(tuple1, tuple2) #Compares
elements of both tuples.
2 len(tuple) #Gives the total length
of the tuple.
3 max(tuple) #Returns item from the
tuple with max value
4 min(tuple) # Returns item from
the tuple with min value

19.  Unordered collection of key-value pairs.
Keys and values can be of any type in dictionary
 Items in dictionaries are enclosed in the curly-
braces {},Separated by the comma (,)
 A colon is used to separate key from value

20. >>>dict1={1:”first”,”second”:2}
>>>dict1[3]=“third line” #add new item
>>>dict1
>>>dict1.keys() # display dictionary keys
>>>dict1.values() # display dictionary values

21. The True and False data is known as Boolean
Practice:
>>>A=True
>>>type(A)
>>>B=False
>>>type(B)

22. >>>name = input(“What is your name?”)
>>>print (“Hello”+name)
>>>age=input(“Enter your age?”)
>>>age
>>>hobbies=input(“What are your hobbies?”)
>>>hobbies

23.  Write a program to print your name, age,and
name of the school.
 Write a program to find the area of a
rectangle/square

25.  If
 If..else
 Nested if

27. if test expression:
statement(s)
• Here, the program evaluates the test expression and will
execute statement(s) only if the text expression is True.
• If the text expression is False, the statement(s) is not
executed.

28. num = 3
if num > 0:
print(num, "is a positive number.")
print("This is always printed.")
num = -1
if num > 0:
print(num, "is a positive number.")

30. Syntax of if...else
if test expression:
Body of if
else:
Body of else

31. # Program checks if the number is positive or
negative
# And displays an appropriate message
num = 3
if num >0:
print("Positive number")
else:
print("Negative number")

33. Syntax of if...elif...else
if test expression:
Body of if
elif test expression:
Body of elif
else:
Body of else

34. # In this program,we check if the number is positive or
negative or zero and display an appropriate message
num = 3.4
if num > 0:
print("Positive number")
elif num == 0:
print("Zero")
else:
print("Negative number")

35. num = float(input("Enter a number: "))
if num >= 0:
if num == 0:
print("Zero")
else:
print("Positive number")
else:
print("Negative number")

36.  Looping is defined as repeatedly executing block of
statements for certain number of times.
 Python has mainly 2 types of looping statements
> for loop
> while loop
 The for loop in Python is used to iterate over a
sequence (list, tuple, string) or other iterable objects.
Iterating over a sequence is called traversal.

37. for val in sequence:
Body of for
• Here, val is the variable that takes the value of the item
inside the sequence on each iteration.
• Loop continues until we reach the last item in the sequence.
The body of for loop is separated from the rest of the code
using indentation.

38. # Program to find the sum of all numbers
stored in a list
# List of numbers
numbers = [6, 5, 3, 8, 4, 2, 5, 4, 11]
# variable to store the sum
sum = 0
# iterate over the list
for val in numbers:
sum = sum+val
print("The sum is", sum)

39.  A for loop can have an optional else block as well.
The else part is executed if the items in the sequence
used in for loop exhausts.
 A for loop's else part runs if no break occurs.

40. digits = [0, 1, 5]
for i in digits:
print(i)
else:
print("No items left.")

41. The while loop in Python is used to iterate over a block of
code as long as the test expression (condition) is true.

42. while test_expression:
Body of while
• In while loop, test expression is checked first. The body of the loop
is entered only if the test_expression evaluates to True. After one
iteration, the test expression is checked again. This process
continues until the test_expression evaluates to False.
• In Python, the body of the while loop is determined through
indentation.
• Body starts with indentation and the first unindented line marks the
end.

43. # Program to add natural numbers upto sum = 1+2+3+...+n
# To take input from the user,
# n = int(input("Enter n: "))
n = 10
# initialize sum and counter
sum = 0
i = 1
while i <= n:
sum = sum + i
i = i+1 # update counter
# print the sum
print("The sum is", sum)

44. THANK YOU