2. Value
• A value is one of the fundamental things, like
a number, a character or a string that program
manipulates.
Example
2,42.0,’Hello,World’ The value belong to
different types.
3. Literal Constants
The value of a literal constant can be used directly in programs. For example,
7, 3.9, 'A', and "Hello" are literal constants.
Numbers refers to a numeric value. You can use four types of numbers in
Python program- integers, long integers, floating point and complex numbers.
Numbers like 5 or other whole numbers are referred to as integers. Bigger
whole numbers are called long integers. For example, 535633629843L is a
long integer.
Numbers like are 3.23 and 91.5E-2 are termed as floating point numbers.
Numbers of a + bi form (like -3 + 7i) are complex numbers.
9/5/2022 Introduction to python 3
4. Example
9/5/2022 Introduction to python 4
Strings
A string is a group of characters.
• Using Single Quotes ('): For example, a string can be written as 'HELLO'.
• Using Double Quotes ("): Strings in doubles are exactly same as those in
single quotes. Therefore, 'HELLO' is same quoteas "HELLO".
• Using Triple Quotes (''' '''): You can specify multi-line strings using triple
quotes. You can use as many single quotes and double quotes as you
want in a string within triple quotes.
Examples:
5. • 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 standard data types supported by python
includes:
– Number
– Boolean
– String
– List
– Tuple
– Dictionary
6. Numbers
• Numbers refers to a numeric value. It includes integers, long
integers, floating point, and complex numbers.
• Integers are whole numbers with no fractional parts. They can be
either positive, negative or zero value. Python displays long
integers with an uppercase L (56788333354533L is a long integer).
• 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’.
• A 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.
7. • 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.
Example:
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 number?", isinstance(1+2j,complex))
Output:
5 is of type <class 'int'>
2.0 is of type <class 'float'>
(1+2j) is complex number? True
8. • Boolean is another data type in Python.
• A variable of Boolean type can have one of the
two values- True or False.
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 [ ].
9. >>> a = [1, 2.2, 'python'] The slicing operator [ ] is
used to extract an item or a range of items from a
list. Index starts form 0 in Python.
Example:
>>>a = [5,10,15,20,25,30,35,40]
>>>a[2]
15
>>>print("a[0:3] = ", a[0:3])
[5,10,15]
10. • 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.
12. 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.
13. Example:
s = 'Hello world!'
print("s[4] = ", s[4]) # s[4] = 'o'
print("s[6:11] = ", s[6:11]) # s[6:11] = 'world'
Output:
s[4] = o
s[6:11] = world
