IMP PPT- Python programming fundamentals.pptx

Chapter - 3
Python programming
fundamentals

Introduction
A Python program is called a script.
Script is a sequence of definitions and commands.
These commands are executed by Python interpreter
known as PYTHON SHELL.
In python programming,
 data types are inbuilt hence support “dynamic
typing”
 declaration of variables is not required.
 memory management is automatically done.

Variables
A variable is like a container that stores values that you
can access or change.
A variable has three main components:
a)Identity of variable
b)Type of variable
c)Value of variable

Variables
a) Identity of the variable
It refers to object’s address in the memory.
>>> x=10
e.g. >>> id (x)

Data Type
b) Type of the variable
Type means data type of a variable.
1. Number: It stores numerical values.
Python supports three built in numeric
types – integer,
floating point numbers and
complex numbers.

Data Type
a. int (integer): Integer represents whole
numbers. (positive or negative)
e.g. -6, 0, 23466
b. float (floating point numbers): It
represents numbers with decimal
point.
e.g. -43.2, 6.0
c. Complex numbers: It is made up of pair
of real and imaginary number.
e.g. 2+5j

Data Type
2. String (str): It is a sequence of
characters. (combination of letters,
numbers and symbols).
It is enclosed within single or double
quotes.
e.g. (‘ ’ or “ ”)
>>> rem= “Hello Welcome to Python”
>>> print (rem)
Hello Welcome to Python

Data Type
3. Boolean (bool): It represents one of the
two possible values – True or False.
>>> bool_1 = (6>10)
>>> print (bool_1)
False
>>> bool_2 = (6<10)
>>> print (bool_2)
True

Data Type
4. None: It is a special data type with single
value.
It is used to signify absence of value
evaluating to false in a situation.
>>> value_1 = None
>>> print (value_1)
None

type() – if you wish to determine type of the
variable.
e.g.
>>> type(10)
<class ‘int’>
>>> type(8.2)
<class ‘float’>
>>> type(“hello”)
<class ‘str’>
>>> type(True)
<class ‘bool’>
Data Type

Value
c) Value of variable
Values are assigned to a variable using
assignment operator (=)..
e.g.
>>>marks=87
>>>print(marks)
87
marks – Name of the variable
Value of the variable
87

Value
The concept of assignment:
There should be only one variable on the left-hand side of
assignment operator.
This variable is called Left value or L-value
There can be any valid expression on the right-hand side of
assignment operator.
This variable is called Right value or R-value
L-value = R-value
Value_1 = 100
Variable Assignment
operator
Value

Value
Multiple assignments:
We can declare multiple variables in a
single statement.
e.g.
>>>x, y, z, p = 2, 40, 30.5, ‘Vinay’

Variable Naming Convention
1. A variable name can contain letter, digits and underscore (_). No
other characters are allowed.
2. A variable name must start with an alphabet or and underscore (_).
3. A variable name cannot contain spaces.
4. Keyword cannot be used as a variable name.
5. Variable names are case sensitive. Num and num are different.
6. Variable names should be short and meaningful.
Invalid variable names – 3dgraph, roll#no, first name, d.o.b, while

Input/Output
Python provides three functions for getting
user’s input.
1. input() function– It is used to get data in
script mode.
The input() function takes string as an
argument.
It always returns a value of string type.

Input/Output
2. int() function– It is used to convert input string
value to numeric value.
3. float() function – It converts fetched value in float
type.
4. eval() – This function is used to evaluate the value
of a string.
It takes input as string and evaluates this string as
number and return numeric result.
NOTE : input() function always enter string value in
python 3. So on need int(), float() function can be
used for data conversion.

Sample Program
n1 = input("Enter first number")
n2 = input("Enter second number")
Sum=n1+n2
print("Sum is:", Sum)

Sample Program
n1 = eval(input("Enter first number"))
n2 = eval(input("Enter second number"))
Sum=n1+n2
n1 = int(input("Enter first number"))
n2 = int(input("Enter second number"))
Sum=n1+n2

To calculate simple interest
p = int(input("Enter Principal:"))
r = float(input("Enter Rate:"))
t = int(input("Enter Time:"))
si=0.0
si=(p*r*t)/100
print("Simple Interest is:", si)

m1 = int(input("Enter marks in English:"))
m2 = int(input("Enter marks in Hindi:"))
m3 = int(input("Enter marks in Maths:"))
m4 = int(input("Enter marks in Science:"))
m5 = int(input("Enter marks in Social Science:"))
total=m1+m2+m3+m4+m5
per = total/5
print("Total is:", total)
print("Percenatge is:", per)
To calculate total and percentage

Python Character Set
A set of valid characters recognized by python.
• Python uses the traditional ASCII character set.
• The latest version recognizes the Unicode character set.
The ASCII character set is a subset of the Unicode
character set.
Letters: a-z, A-Z
Digits : 0-9
Special symbols : Special symbol available over keyboard
White spaces: blank space, tab, carriage return, new
line, form feed
Other characters: Unicode

Tokens
Smallest individual unit in a program is
known as token.
1. Keywords
2. Identifiers
3. Literals
4. Operators
5. Delimiters

1. Keywords
Reserved word of the compiler/interpreter which can’t
be used as identifier.

2. Identifiers
A Python identifier is a name used to
identify a variable, function, class,
module or other object.

3. Literals
Literals in Python can be defined as number,
text, or other data that represent values to be
stored in variables.
Example of String Literals in Python
name = ‘Johni’ , fname=“johny”
Example of Integer Literals in Python(numeric literal)
age = 22
Example of Float Literals in Python(numeric literal)
height = 6.2
Example of Special Literals in Python
name = None

3. Literals
Escape sequence
e.g.
print(“I am a student of n APS t Yol Cantt”)

4. Operators
Operators can be defined as symbols that are used to
perform operations on operands.
Types of Operators
a. Arithmetic Operators.
b. Relational Operators.
c. Assignment Operators.
d. Logical Operators.
e. Membership Operators
f. Identity Operators

4. Operators
a. Arithmetic Operators.
Arithmetic Operators are used to perform arithmetic
operations like addition, multiplication, division etc.

print ("hello"+"python")
print(2+3)
print(10-3)
print(22%5)
print(19//5)
print(2**3)
Output:
hellopython
5
7
2
3
8

4. Operators
b. Relational Operators.
Relational Operators are used to compare the values.

print(5==3) False
print(7>3) True
print(15<7) False
print(3!=2) True
print(7>=8) False
print(3<=4) True

4. Operators
c. Assignment Operators.
Used to assign values to the variables.

a=10
print(a)
a+=9
print(a)
b=11
b*=3
print(b)
c=19
c/=2
print(c)
d=2
d**=4
print(d)
Output:
10
19
33
9.5
16

4. Operators
d. Logical Operators.
Logical Operators are used to perform logical operations
on the given two variables or values.
a=30
b=20
if(a==30 and b==20):
print("hello")
Output :-
hello
a=70
b=20
if(a==30 or b==20):
print("hello")

4. Operators
e. Membership Operators
It used to validate whether a value is found within a
sequence such as such as strings, lists, or tuples.
E.g.
a = 22
list = [11, 22,33,44]
ans= a in list
print(ans)
Output: True
E.g.
a = 22
list = [11, 22,33,44]
ans= a not in list
print(ans)
Output: False

4. Operators
f. Identity Operators
Identity operators in Python compare the memory
locations of two objects.

IMP PPT- Python programming fundamentals.pptx

5. Delimiters
These are the symbols which can be used as
separator of values or to enclose some values.
e.g ( ) { } [ ] , ; :

Token Category
X Variable
y Variable
z Variable
print Keyword
( ) Delimiter
/ Operator
68 Literal
“x, y, z” Literal

Comments
Comments are statements in the script that are
ignored by the Python interpreter.
Comments (hash symbol = #) makes code more
readable and understandable.
# Program to assign value
x=10
x=x+100 # increase value of x by 100
print(x)

Expressions
Expressions are combination of value(s). i.e.
constant, variable and operators.
Expression Value
5+2*4 13
8+12*2-4 28
Converting mathematical expression to
equivalent Python expression
Algebraic Expression Python Expression
y = 3 (
𝑥
2
) y = 3 * x / 2
z= 3bc + 4 z = 3*b*c + 4

User Defined Functions
A function is a group of statements that exists
within a program for the purpose of performing a
specific task.
Syntax:
def function_name(comma_sep_list_parameters):
statements

User Defined Functions
Example 1:
def display():
print(“Welcome to pyhton”)
>>>display()
Example 2:
def arearec(len, wd):
area=len*wd
return area
>>>arearec(30, 10)

IMP PPT- Python programming fundamentals.pptx

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