Values and Data types in python

Values and Data types
in Python
Prepared By,
P.Jothi Thilaga, AP/CSE
Ramco Institute of Technology
Rajapalayam

Value
one of the fundamental things, like a number, a
character or a string that program manipulates.
Example: a = 25, b= “Hi”
25, Hi represents values
Data type
refers to the type and size of data. Variables can
hold values of different data types. Python is a
purely object oriented language. It refers to
everything as an object, including numbers and
strings.

The five standard data types supported by python
includes:
Number
String
List
Tuple
Dictionary

Numbers
Number refers to a numeric value.
It includes
 integers
 long integers
 floating point
 complex numbers

Integers are whole numbers with no fractional parts.
They can be either positive, negative or zero value.
Long integers in python is displayed with an
uppercase L (56788333354533L is a long integer). -
supported only in python 2 version not in python 3.
Floating point numbers are numbers with fractions
or decimal points. Floating point values can be
expressed in scientific notation using the letter ‘e’ or
‘E’.
Complex number is a number that can be expressed
in the form a + bi, where a and b are real numbers,
and i is the imaginary unit.

Boolean is another data type in Python.
A variable of Boolean type can have one of
the two values - True or False.
The type() function can be used to know which data
type a variable or a value belongs to.
The isinstance() function to check if an object
belongs to a particular class.

Examples:
a = 5
print(a, "is of type", type(a))
a = 2.0
print(a, "is of type", type(a))
a = 1+2j
print(a, "is complex no.?", isinstance(1+2j,complex))
Output:
5 is of type <class 'int'>
2.0 is of type <class 'float'>
(1+2j) is complex no.? True

List
List is an ordered sequence of items. It is one
of the most used data type in Python and is
very flexible.
All the items in a list do not need to be of the
same type.
Lists are mutable. The elements in the list can
be modified.
To declare a list in python, separate the items
using commas and enclose them within square
brackets [ ].

>>> a = [1, 2.2, 'python'] The slicing operator [ ] is used
to extract an item or a range of items from a list. Index
starts from 0 in Python.
Examples:
>>>a = [5,10,15,20,25,30,35,40]
>>>a[2]
15
>>>print("a[0:3] = ", a[0:3])
a[0:3] = [5, 10, 15]

Tuple
Tuple is an ordered sequence of items same as
list. The only difference is that tuples are
immutable. Tuples once created cannot be
modified.
It is defined within parentheses ( ) where items
are separated by commas.

Example:
>>> t = (5, 'program', 1+3j, 4, 11.5)
print("t[1] = ", t[1])
print("t[0:3] = ", t[0:3])
Output:
t[1] = program
t[0:3] = (5, 'program', (1+3j))

Strings
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.
>>> s = "This is a string"
Strings are immutable.

Examples:
s = 'Hello world!'
print("s[4] = ", s[4])
print("s[6:11] = ", s[6:11])
Output:
s[4] = o
s[6:11] = world

Dictionary
A python dictionary is an unordered collection
of key-value pairs.
Keys and values can be of any type in a
dictionary.
Items in dictionary are separated by comma
and enclosed with the curly-braces { }.
Example:
>>>dict={1:“hi”,2: “hello”}

Exercises
1. --------- are the reserved memory locations that stores
values.
2. What data type is used to store values in terms of key
and value?
(a) list
(b) tuple
(c) class
(d) dictionary
3. What data type is the object below ?
L = [1.0, 15, ‘hi’, 27]
(a) list
(b) dictionary
(c) array
(d) tuple

Answers
1. Variables
2. (d) dictionary
3. (a) list

Values and Data types in python

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