Python for Beginners(v1)

Dr.M.Rajendiran
Dept. of Computer Science and Engineering
Panimalar Engineering College

Install Python 3 On Ubuntu
Prerequisites
Step 1.A system running Ubuntu
Step 2.A user account with sudo privileges
Step 3.Access to a terminal command-line (Ctrl–Alt–T)
Step 4.Make sure your environment is configured to use
Python 3.8
2

Install Python 3
Now you can start the installation of Python 3.8.
$sudo apt install python3.8
Allow the process to complete and verify the Python
version was installed successfully
$python ––version
3

Installing and using Python on Windows is very simple.
Step 1: Download the Python Installer binaries
Step 2: Run the Executable Installer
Step 3: Add Python to environmental variables
Step 4: Verify the Python Installation
4

Python Installation
Open the Python website in your web browser.
https://www.python.org/downloads/windows/
Once the installer is downloaded, run the Python installer.
Add the following path
C:Program FilesPython37-32: for 64-bit installation
Once the installation is over, you will see a Python Setup
Successful window.
You are ready to start developing Python applications in
your Windows 10 system.
5

Introduction
Python is a general-purpose interpreted, interactive, object-
oriented, and high-level programming language.
It was created by Guido van Rossum during 1985- 1990.
Python got its name from “Monty Python’s flying circus”.
Python was released in the year 2000.
Python is interpreted
Python is processed at runtime by the interpreter.
You do not need to compile your program before executing it.

Introduction
Python is Interactive: You can actually sit at a Python
prompt and interact with the interpreter directly to write your
programs.
Python is Object-Oriented: Python supports Object-
Oriented style or technique of programming that
encapsulates code within objects.
Python is a Beginner's Language: Python is a great
language for the beginner level programmers and supports
the development of a wide range of applications.

Features
Easy-to-learn
Easy-to-maintain
Portable
Interpreted
Extensible
Free and Open Source
High Level Language
Scalable

Applications
Bit Torrent(a stream flowing with great force) file
sharing
Google search engine, YouTube
Intel, Cisco, HP, IBM
i–Robot
NASA(National Aeronautics and Space Administration)
Facebook, Drop box

Applications
Python interpreter:
1.Interpreter
To execute a program in a high-level language by
translating it one line at a time.
2.Compiler
To translate a program written in a high-level language into
a low-level language all at once, in preparation for later
execution.

Modes of python interpreter
Python Interpreter is a program that reads and executes
python code. It uses two modes of execution.
1. Interactive mode
2. Script mode
1.Interactive mode
Interactive Mode, as the name suggests, allows us to interact
with operating system.
When we type python statement, interpreter displays the
result(s) immediately.

Advantages:
Python, in interactive mode, is good enough to learn,
experiment or explore.
Working in interactive mode is convenient for beginners
and for testing small pieces of code
Drawback:
We cannot save the statements and have to retype all the
statements once again to re-run them.
In interactive mode, you type python programs and the
interpreter displays the result.

2.Script mode
In script mode, we type python program in a file and then
use interpreter to execute the content of the file.
Scripts can be saved to disk for future use.
Python scripts have the extension .py, meaning that the
filename ends with .py
Save the code with filename.py and run the interpreter in
script mode to execute the script.

Integrated Development Learning Environment (IDLE)
It a graphical user interface which is completely written in
python.
It is bundled with the default implementation of the python
language and also comes with optional part of the python
packaging.
Features
Multi-window text editor with syntax highlighting.
Auto completion with smart indentation.
Python shell to display output with syntax highlighting.

VALUES AND DATA TYPES
Values
Value can be any letter, number or string.
Values are different data types
Eg: 2, 42.0, and 'Hello, World!'.
Data type
Every value in python has a data type.
It is a set of values, and the allowable operations on those
values.
Python has five standard data types:

1.Numbers
 It stores numerical values.
 This data type is immutable (i.e. values/items cannot be changed).
Python supports following number types
1. Integers
2. Floating point numbers
3. Complex numbers.

1.1Integer
Integers are the whole numbers consisting of positive(+ve) or negative(–
ve) sign.
Integers can be any length, it is only limited by the memory available
Example:
a=10
a=eval(input(“enter a value”))
a=int(input(“enter a value”))
1.2 Float
It has decimal part and fractional part.
It is accurate upto 15 decimal places.

Example:
a=3.15
a=float(input(“enter a value”))
1.3 Complex
It is a combination of real and imaginary part.
Example:
2+5j
a+bi

2.Boolean
Boolean data type have two values. It has either 0 or 1.
0 means False
1 means True
True and False is a keyword.
Example:
>>> 3==5
False
>>> True+True
2
>>> False+True
1
>>> False*True
0

3.Sequence
 A sequence is an ordered collection of items, indexed by positive
integers.
 It is a combination of mutable (value can be changed) and immutable
(values cannot be changed) data types.
There are three types of sequence data type available in python, they are
1. Strings
2. Lists
3. Tuples

3.1 Strings
 String is defined as a continues set of characters represented in
quotation marks (either single quotes ( ‘ ) or double quotes ( “ ).
 An individual character in a string is accessed using a subscript (index).
 The subscript should always be an integer (positive or negative).
 A subscript starts from 0 to n-1.
 Strings are immutable i.e. the contents of the string cannot be changed
after it is created.
 Python will get the input at run time by default as a string.
 Python does not support character data type. A string of size 1 can
be treated as characters.

1. single quotes (' ')
2. double quotes (" ")
3. triple quotes(“”” “”””)
Operations on string
1. Indexing
2. Slicing
3. Concatenation
4. Repetitions
5. Member ship

.
Indexing >>>a=”HELLO”
>>>print(a[0])
>>>H
>>>print(a[1])
>>>O
Positive indexing helps in accessing the
string from the beginning.
Negative subscript helps in accessing the
string from the end.
Slicing
print[0:4] – HELL
print[ :3] – HEL
print[0: ]
HELLO
The slice[n : m] operator extracts sub string
from the strings.
A segment of a string is called a slice.
Concatenation
a=”raj”
b=”man”
print(a+b)
rajman
The + operator joins the text on both sides
of the operator.
Repetitions
a=”welcome ”
print(a*3)
welcome welcome
welcome
The * operator repeats the string on the left
hand side times the value on right hand
side.
Membership
>>> s="good morning"
>>>"m" in
s True
>>> "a" not in
s True
Using membership operators to check a
particular character is in string or not.
Returns true if present

3.2 Lists
 List is an ordered sequence of items. Values in the list are called
elements or items.
 Values are separated by commas and enclosed within square
brackets[].
 Items in the lists can be different data types.
 Lists are mutable(values of list can be changed)
Operations on list
1. Indexing
2. Slicing
3. Concatenation
4. Repetitions

.create a list
>>> a=[2,3,4,5,6,7,8,9,10]
>>> print(a)
[2, 3, 4, 5, 6, 7, 8, 9, 10]
This is way we can create a list
at compile time
Indexing
>>>print(a[0])
2
>>> print(a[8])
10
>>> print(a[1])
10
Accessing the item in the
position 0
position 8
Accessing a last element
using negative indexing.
Slicing
>>> print(a[0:3])
[2, 3, 4]
>>> print(a[0:])
[2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> print(a[:8])
[2, 3, 4, 5, 6, 7, 8, 9]
Printing a part of the string.
Concatenation
>>>b=[20,30]
>>> print(a+b)
[2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30]
Adding and printing the items of
two lists.
Repetition
>>> print(b*3)
[20, 30, 20, 30, 20, 30]
Create a multiple copies of the
same string.

. Updating the list
>>> print(a[2])
4
>>> a[2]=100
>>> print(a)
[2, 3, 100, 5, 6, 7, 8, 9, 10]
Updating the list using index
value
Inserting an
element
>>> a. insert(0,“tham")
>>> print(a)
a=[“tham”,2,3,4,5,6,7,8,9,10]
Inserting an element in 0th
position
Removing an
element
>>> a. remove(“tham”)
>>> print(a)
a=[2,3,4,5,6,7,8,9,10]
Removing an element
by giving the element directly

3.3Tuple
 A tuple is an ordered sequence of items same as list.
 The set of elements is enclosed in parenthesis instead of square
brackets.
 A tuple is an immutable. i.e. cannot be modified.
 Tuples are faster than lists.
 Tuples can be used as keys in dictionaries.
 Tuples are used to write-protect data and cannot be change
dynamically
 Tuple have no append or extend method.
 Elements can not be removed from a tuple.

Operations on Tuple
1. Indexing
2. Slicing
3. Concatenation
4. Repetitions

.
Creating a tuple
>>>a=(20,40,60,”apple”,”ball”)
Creating the tuple with
elements of different data
types.
Indexing
>>>print(a[0])
20
>>> a[2] 60
position 0
position 2
Slicing
>>>print(a[1:3])
(40,60)
Displaying items from 1st till
2nd.
Concatenation
>>> b=(2,4)
>>>print(a+b)
>>>(20,40,60,”apple”,”ball”,2,4)
Adding tuple elements at the
end of another tuple
elements
Repetition
>>>print(b*2)
>>>(2,4,2,4)
repeating the tuple in n no of
times
updating a tuple
>>>a[2]=100
Type Error: 'tuple' object does
not support item assignment
Altering the tuple data type
leads to error.

4.Dictionaries
Dictionaries are unordered sets.
Dictionary is created by using curly braces. i,e. { }
Dictionaries are accessed via keys.
A dictionary is an associative array. Any key of the
dictionary is associated (or mapped) to a value.
The values of a dictionary can be any Python data type. So
dictionaries are key value-pairs
Dictionaries don't support the sequence data types like
strings, tuples and lists.

5.Sets
The set datatype is an unordered collection of unique items
The collection is mutable.(i.e. can be add or remove)
Set is defined by value separated by comma inside curly
braces.{}
It has no duplicate entry.
Creating a
dictionary
>>>a={'name':"abi",'age':18,'mark':1
00}
>>>print(a)
{'name': 'abi', 'age': 18, 'mark': 100}
Creating the dictionary
with elements of different
data
types.
Indexing
>>>print(a['name'])
abi
Accessing the item with
keys.

Example:
a={1,2,3,4,5,6,7,6,7}
print(a)
a={1,2,3,4,5,6,7}
Scalar type
A scalar is a type that can have a single value such as 5,3.14, “THAM”
Example: int, float, complex, boolean and string
Escape sequence
n – move to newline
t – move one tap space horizontally
v – move in space vertically
b – back space

VARIABLES
A variable is an identifier that refers to a value
While creating a variable, memory space is reserved in memory
Based on the data type of a variable, the interpreter allocates
memory
The assignment statements are used to create a new variable
and assign values to them.
Variable names can contain letters, underscore and numbers but
do not start with numbers.
Underscore(_) can be used in variable names.
Example:
a=5 // single assignment
a,b,c=2,3,4 // multiple assignment
a=b=c=2 //assigning one value to multiple variables

KEYWORDS
Keywords are the reserved words in python.
We cannot use a keyword as variable name, function name or any
other identifier.
They are used to define the syntax and structure of the python
language.
Keywords are case sensitive.

IDENTIFIERS
Identifier is the name given to entities like class, functions,
variables etc. in python.
Identifiers can be a combination of letters in lowercase (a to z) or
uppercase (A to Z) or digits (0 to 9) or an underscore (_).
An identifier cannot start with a digit.
Keywords cannot be used as identifiers.
Cannot use special symbols like !, @, #, $, % etc. in our
identifier.
Identifier can be of any length.
Valid Identifiers
num,Num,Num1,_num,num_temp2,IF,Else
Invalid Identifiers
Num 1,num 1,addition of program,1Num,num.no,if,else

STATEMENTS
Instructions that a python interpreter can executes are called
statements.
A statement is a unit of code like creating a variable or displaying a
value.
>>> n = 17
>>> print(n)
Here, The first line is an assignment statement that gives a value to n.
The second line is a print statement that displays the value of n.
There are two types of statements available
1. single line statements
2. multi line statements

STATEMENTS
1.Single line statements
single line statements are end with newline
Examples:
a=1
b=2
c=a+b
2.Multiline statements
python allows the user to write multi line statement using line
continuation character () to denote that the line should continue.
Example:
total=mark1+
mark2+
mark3

INPUT AND OUTPUT
INPUT
Input is a data entered by user in the program.
In python, input () function is available for input.
Syntax:
variable = input (“data”)
Example:
a=input("enter the name:")
Data type Compile time Run time
int a=10 a=int(input(“enter a”))
float a=10.5 a=float(input(“enter a”))
string a=”panimalar” a=input(“enter a string”)
list a=[20,30,40,50] a=list(input(“enter a list”))
tuple a=(20,30,40,50) a=tuple(input(“enter a tuple”))

INPUT AND OUTPUT
OUTPUT
An output can be displayed to the user using print statement.
Syntax:
print (expression/constant/variable)
Example:
print ("Hello") // Hello
print(5) //5
print(3+5) //8
print(c)

COMMENTS
Comments are used to provide more details about the program like
name of the program, author of the program, date and time, etc.
Types of comments
1. Single line comments
2. Multi line comments
1.Single line comments(#)
A hash sign (#) is the beginning of a comment.
Anything written after # in a line is ignored by interpreter.
Example:
Percentage = (minute * 100) / 60 # calculating percentage of an hour

COMMENTS
2.Multi line comments(“””……”””)
Multiple line comments can be written using triple quotes “”” ……….”””
Example:
“”” This program is created by Robert in Dell lab on 12/12/20 based on
newtons method”””

LINES AND INDENTATION
Most of the programming languages like C, C++, Java use braces { }
to define a block of code. But, python uses indentation.
Blocks of code are denoted by line indentation.
It is a space given to the block of codes for class and function
definitions or flow control.
Example:
a=3
b=1
if a>b:
print("a is greater")
else:
print("b is greater")

TUPLE ASSIGNMENT
A tuple using a single assignment statement.
Python has a very powerful tuple assignment.
Tuple of variables on the left to be assigned values from a tuple on
the right.
The left side is a tuple of variables, the right side is a tuple of values.
Each value is assigned to its respective variable.
All the expressions on the right side are evaluated before any of the
assignments.
(a,b,c)=(3,4,5)
(a, b, c, d) = (1, 2, 3)
ValueError: need more than 3 values to unpack Swapping two
numbers using tuple
(a, b) = (b, a)

OPERATORS
An operator is symbol that tells the compiler to perform specific
mathematical or logical manipulations.
Consider the expression 4 + 5 = 9. Here, 4 and 5 are called
operands and + is called operator.
Types of Operators
1. Arithmetic Operators
2. Comparison (Relational) Operators
3. Assignment Operators
4. Logical Operators
5. Bitwise Operators
6. Membership Operators
7. Identity Operators

OPERATORS
Arithmetic operators
They are used to perform mathematical operations like addition,
subtraction, multiplication etc.
Operator Description
Example
a=9,b=2
+ Addition Adds values on either side of the operator. a + b = 11
- Subtraction Subtracts operand. Right hand operand from left hand a – b = 7
* Multiplication Multiplies values on either side of the operator a * b = 18
/ Division Divides left hand operand by right hand operand b / a = 4
% Modulus
Divides left hand operand by right hand operand and
returns remainder
b % a = 1
** Exponent
Performs operators exponential (power) calculation on
operators
a**b =9 to the
power 2
//
Floor Division The division of operands where the
result is the quotient in which the digits after the
decimal point are removed
5//2=4.0

OPERATORS
Comparison (Relational) Operators
Comparison operators are used to compare values.
It either returns True or False according to the condition.
Example
a=10,b=20
==
If the values of two operands are equal, then the condition becomes
true.
(a == b)
is not true.
!= If values of two operands are not equal, then condition becomes true. (a!=b)
is true
>
If the value of left operand is greater than the value of right operand,
then condition becomes true.
(a > b)
is not true.
<
If the value of left operand is less than the value of right operand,
then condition becomes true.
(a < b)
is true.
>=
If the value of left operand is greater than or equal to the value of
right operand, then condition becomes true.
(a >= b)
is not true.
<=
If the value of left operand is less than or equal to the value of right
operand, then condition becomes true.
(a <= b)
is true.

OPERATORS
Assignment Operators
Assignment operators are used in Python to assign values to
variables.
Operator Description Example
=
Assigns values from right side operands to left side
operand.
c = a + b
assigns value of
a + b into c
+= Add AND
It adds right operand to the left operand and assign
the result to left operand
c += a
is equivalent to
c= c + a
= Subtract AND
It subtracts right operand from the left operand and
assign the result to left operand
c = a
is equivalent to
c= c a
*= Multiply AND
It multiplies right operand with the left operand and
c *= a
is equivalent to
c= c * a
/= Divide AND
It divides left operand with the right operand and
c /= a
is equivalent to
c= c / ac

OPERATORS
Logical Operators
Logical operators are and, or, not operators.
.
%= Modulus AND
It takes modulus using two operands and assign the
result to left operand
c %= a is
equivalent to c
= c % a
**= Exponent AND
Performs exponential (power) calculation on
operators and assign value to the left operand
c **= a is
equivalent to c
= c ** a
//= Floor Division
It performs floor division on operators and assign
value to the left operand
c //= a is
equivalent to c
= c // a
Operator Meaning Example
and True if both the operands are true x and y
or True if either of the operands is true x or y
not True if operand is false (complements the operand) not x

OPERATORS
Bitwise Operators
Bitwise operators act on operands as if they are binary digits. They
operate bit by bit.
Let x = 10 (0000 1010) and y = 4 (0000 0100)
& Bitwise AND x & y = 0 (0000 0000)
| Bitwise OR x | y = 14 (0000 1110)
~ Bitwise NOT ~x = -11 (1111 0101)
^ Bitwise XOR x ^ y = 14 (0000 1110)
>> Bitwise right shift x >> 2 = 2 (0000 0010)
<< Bitwise left shift x << 2 = 40 (0010 1000)

OPERATORS
Membership Operators
Evaluates to find a value or a variable is in the specified sequence
of string, list, tuple, dictionary or not.
Let, x=[5,3,6,4,1]. To check particular item in list or not, in and not in
operators are used.
Example:
x=[5,3,6,4,1]
>>> 5 in x
True
>>> 5 not in x
False
in True if value/variable is found in the sequence 5 in x
not in
True if value/variable is not found in the
sequence
5 not in x

OPERATORS
Identity Operators
They are used to check if two values (or variables) are located on
the same part of the memory.
Example
x = 5
y = 5
a = 'Hello'
b = 'Hello'
print(x is not y) // False
print(a is b)//True
is True if the operands are identical x is True
is not True if the operands are not identical x is not True

Operator Precedence
When an expression contains more than one operator, the order of
evaluation depends on the rules of precedence.
() Parenthesis
** Exponentiation (raise to the power)
~ + - Complement, unary plus and minus
* / % // Multiply, divide, modulo and floor division
+ - Addition and subtraction
>> << Right and left bitwise shift
& Bitwise 'AND'
^ | Bitwise exclusive `OR' and `OR'
<= < > >= Comparison operators
<> == != Equality operators
= %= /= //= -= += *= **= Assignment operators
Is, is not Identity operators
In, not in Membership operators
and,or,not Logical operators

Expressions
An expression is a combination of values, variables, and operators.
A value and a variable itself considered as an expression.
The following are all legal expressions:
>>> 42
42
>>> a=2
>>> a+3+2
7
>>> z=("hi"+"friend")
>>> print(z)
hifriend

FUNCTIONS
Function is a sub program which consists of set of instructions used
to perform a specific task.
A large program is divided into number of sub program called
function.
Need for Function
When the program is too complex and large they are divided into
sub program.
Each sub program is separately coded and combined into single
program. Each subprogram is called as function.
Debugging, Testing and maintenance becomes easy when the
program is divided into subprograms.
Functions are used to avoid rewriting same code again and again in
a program.
Function provides code re-usability
The length of the program is reduced.

FUNCTIONS
TYPES OF FUNCTION
1. Built in function
2. user defined function
1.Built in function
Built in functions are the functions that are already created and
stored in python.
These built in functions are always available for usage and
accessed by a programmer.
It cannot be modified.

FUNCTIONS
.
Built in function Description
>>>max(3,4)
4 # returns largest element
>>>min(3,4)
3 # returns smallest element
>>>len("hello")
5 #returns length of an object
>>>range(2,8)
[2, 3, 4, 5, 6, 7] #returns range of given values
>>>round(7.8)
8.0 #returns rounded integer of the given number
>>>chr(5)
x05' #returns a character (a string) from an integer
>>>float(5)
5.0 #returns float number from string or integer
>>>int(5.0)
5 # returns integer from string or float
>>>pow(3,5)
243 #returns power of given number
>>>type( 5.6)
<type 'float'> #returns data type of object to which it belongs
>>>t=tuple([4,6.0,7])
>>>t
(4, 6.0, 7)
# to create tuple of items from list
>>>print("good morning")
Good morning # displays the given object

FUNCTIONS
2.User defined function
User defined functions are the functions that programmers create for
their requirement and use.
These functions can then be combined to form module which can be
used in other programs by importing them.
Advantages
The programmer can write their own functions which are known as
user defined function.
These functions can create by using keyword def.
Example:
add(), sub()
Elements of User defined function
There are two elements in user defined function.
1. function definition
2. function call

FUNCTIONS
1.Function definition
A function definition specifies the name of a new function and the
sequence of statements that execute when the function is called.
Syntax:
def function name(parameter list): ----Function header
statement 1
statement 2
....
....
statement n
def is a keyword that indicates that this is a function definition.
The rules for function names are the same as for variable names
The first line of the function definition is called the header, the rest is
called body of function.
The header has to end with a colon and the body has to be indented.
The function contains any number of statements.
Parameter list contains list of values used inside the function.
 Body of the function

FUNCTIONS
Example:
def add():
b=eval(input(“enter a value”))
c=a+b
print(c)
2.Function call()
A function is called by using the function name followed by
parenthesis().
Argument is a list of values provided to the function when the
function is called
The statements inside the function does not executed until the
function is called.
Function can be called n number of times

FUNCTIONS
Syntax:
function name(argument list)
Example:
add() or add(a,b)
Flow of Execution
The order in which statements are executed is called the flow of
execution
Program execution starts from first statement.
One statement is executed at a time from top to bottom.
Function definitions do not alter the flow of execution of the program.
The statement inside the function are not executed until the function
is called.

FUNCTIONS
When a function is called, the control flow jumps to the body of the
function, execute the statements and return back to the place in the
program where the function call was made.

FUNCTION PROTOTYPES
Based on arguments and return type functions are classified into
four types.
1. Function without arguments and without return type
2. Function with arguments and without return type
3. Function without arguments and with return type
4. Function with arguments and with return type

FUNCTION PROTOTYPES
1. Function without arguments and without return type
In this type no argument is passed through the function call and no
output is return to main function
The sub function will read the input values perform the operation and
print the result in the same block.
Example
def add():
a=int(input("enter a"))
b=int(input("enter b"))
c=a+b
print(c)
add()
Output:
enter a 5
enter b 10
15

FUNCTION PROTOTYPES
2. Function with arguments and without return type
Arguments are passed through the function call but output is not
return to the main function.
Example:
def add(a,b):
c=a+b
print(c)
add(a,b)
OUTPUT:
enter a 5
enter b 10
15

FUNCTION PROTOTYPES
3. Function without arguments and with return type
In this type no argument is passed through the function call but
output is return to the main function.
Example:
def add():
c=a+b
return c
c=add()
print(c)
OUTPUT:
enter a 5
enter b 10
15

FUNCTION PROTOTYPES
4. Function with arguments and with return type
In this type arguments are passed through the function call and
output is return to the main function.
Example:
def add(a,b):
c=a+b
return c
c=add(a,b)
print(c)
OUTPUT:
enter a 5
enter b 10
15

FRUITFUL FUNCTION
Fruitful functions are functions that return value or A function that
yields a return value.
Example:
Root=sqrt(25)
Example:
def add():
a=10
b=20
c=a+b
return c
c=add()
print(c)

VOID FUNCTION
Void function is a function that always return none.
It represents the absence of value.
Example:
print("Hello")
Example:
def add():
a=10
b=20
c=a+b
print(c)
add()

PARAMETERS AND ARGUMENTS
Parameters
 Parameters are the value(s) provided in the function header within
parenthesis.
 These are the values required by function to work.
 If there is more than one value, separated by comma.
Example: def add(a,b):
Arguments
 Arguments are the value(s) provided in function call statement.
 List of arguments should be same way as parameters are listed.
 Bounding of parameters to arguments is done 1:1, and there should be
same number and type of arguments as mentioned in parameter list.
Example: add(a,b)

Return Statement
 The return statement is used to exit a function and go back to the place
from where it was called.
 If the return statement has no arguments, then it will not return any
values. But exits from function.
Syntax:
return variable
Example:
def add(a,b):
c=a+b
return c
a=5
b=4
c=add(a,b)
print(c)
No Example Description
1 return a return 1 variable
2 return a,b return 2 variables
3 return a,b,c return 3 variables
4 return a+b return expression
5 return 8 return value

ARGUMENTS TYPES
You can call a function by using the following types of formal arguments
1. Required arguments
2. Keyword arguments
3. Default arguments
4. Variable-length arguments
1.Required Arguments:
 The number of arguments in the function call should match exactly with
the function definition.

. Example Output
def student( name, roll ):
print(name,roll)
student("george",98)
George
98
print(name,roll)
student(101,”rithika”)
101
rithika
print(name,roll)
student(101)
student() missing 1 required
positional
argument: 'name'
print(name,roll)
student()
student() missing 2 required
positional
arguments: ‘name' and ‘roll'

2.Keyword Arguments
 Python interpreter is able to use the keywords provided to match the
values with parameters even though if they are arranged in out of order.
Example Output
def student( name, roll,mark):
print(name,roll,mark)
student (mark=90,roll=102,name="bala")
bala
102
90
def student( name, roll,mark):
student (name="bala", roll=102, mark=90)
bala
102
90

3.Default Arguments
 Assumes a default value if a value is not provided in the function call for
that argument.
 It allows us to miss one or more arguments.
Example Output
def student( name="raja", roll=101,mark=50):
student (mark=90,roll=102,name="bala")
bala
102
90
student (name="bala", roll=102)
bala
102
90
student ()
raja
101
50

4.Variable length Arguments
 If we want to specify more arguments than function header parameter,
variable length arguments are used.
 It is denoted by * symbol before parameter.
Example Output
def student( name,mark):
print(name,mark)
student (“bala”,90)
bala
90
def student( name, roll,*mark):
student ("raja",101,90,80)
raja
101
90
80

MODULES
A module is a file containing python definitions, functions,
statements and instructions.
Standard library of python is extended as modules.
Programmer needs to import the module.
Once we import a module, we can use to any of its functions or
variables in our code.
There is large number of standard modules also available in
python.
Standard modules can be imported the same way as import our
user-defined modules.

MODULE
Two ways to import your module:
1. import keyword
2. from keyword
1.Import keyword
 Import keyword is used to get all functions from the module.
 Every module contains many function.
 To access one of the function , you have to specify the name of the
module and the name of the function separated by dot .
 This format is called dot notation.
Syntax:
import module_name
module_name.function_name(variable)

MODULE
Importing built-in module
import math
x=math.sqrt(25)
print(x)
Importing user-defined module
cal.py
def add(a,b):
c=a+b
return c
import cal
x=cal.add(5,4)
print(x)

MODULE
2.from keyword
 from keyword is used to get only particular function from the module.
Syntax:
from module_name import function_name
#Importing built-in module
from math import sqrt
x=sqrt(25)
print(x)
#Importing user-defined module
from cal import add
x=add(5,4)
print(x)
add.py
def add(a,b):
c=a+b
return c

BUILT-IN MODULES
. Built-in Function Description
math.ceil(x)
Return the ceiling of x, the smallest integer
greater than or equal to x
math.floor(x)
Return the floor of x, the largest integer less
than or equal to x.
math.factorial(x) Return x factorial
math.sqrt(x) Return the square root of x
math.log(x) Return the natural logarithm of x
math.log10(x) Returns the base-10 logarithms
math.log2(x) Return the base-2 logarithms
math.sin(x) Returns sin of x radians
math.cos(x) Returns cosine of x radians

BUILT-IN MODULES
Generate pseudo-random numbers
Random Function Description
random.randrange(stop) Return random numbers from 0
random.randrange(start, stop[,
step])
Return the random numbers in a range
random.uniform(a, b) Return a random floating point number

SAMPLE PROGRAMS
.
Swapping two number Output
a = int(input("Enter a value "))
b = int(input("Enter b value "))
c = a
a = b
b = c
print("a=",a,"b=",b,)
Enter a value 5
Enter b value 8
a=8
b=5
Distance between two points Output
import math
x1=int(input("enter x1"))
y1=int(input("enter y1"))
x2=int(input("enter x2"))
y2=int(input("enter y2"))
distance =math.sqrt((x2-
x1)**2)+((y2-y1)**2)
print(distance)
enter x1 7
enter y1 6
enter x2 5
enter y2 7
2.5

SAMPLE PROGRAMS
.
Circulate n numbers Output
a=list(input("enter the list"))
print(a)
for i in range(1,len(a),1):
print(a[i:]+a[:i])
enter the list '1234'
['1', '2', '3', '4']
['2', '3', '4', '1']
['3', '4', '1', '2']
['4', '1', '2', '3']

Practice
An evaluate the following expressions
No. Expression output
1 a=9-12/3+3*2-1 Ans:a=10
2 A=2*3+4%5-3/2+6 Ans:A=15
3
find m=?
m=-43||8&&0||-2
Ans:m=1
4
a=2,b=12,c=1
d=a<b>c
Ans:d=0
5
a=2,b=12,c=1
d=a<b>c-1
Ans:d=1
6 a=2*3+4%5-3//2+6 Ans:a=15

Python for Beginners(v1)

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