Python for Beginners(v3)

Python for Beginners(v3)
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

iPython Installation
If you already have Python installed, you can use pip to
install iPython using the following command:
$pip install iPython
To use it, type the following command in your computer’s
terminal:
$ipython
6

Compound Data Type
List
 List is an ordered sequence of items. Values in the list are called
elements.
 List of values separated by commas within square brackets[ ].
 Items in the lists can be of different data types.
Tuples
 A tuple is same as list.
 The set of elements is enclosed in parentheses.
 A tuple is an immutable list.
i.e. once a tuple has been created, you can't add elements to a
tuple or remove elements from the tuple.
 Tuple can be converted into list and list can be converted in to tuple.

Compound Data Type
Dictionary
 Dictionary is an unordered collection of elements.
 An element in dictionary has a key: value pair.
 All elements in dictionary are placed inside the curly braces{ }
 Elements in dictionaries are accessed via keys and not by their
position.
 The values of a dictionary can be any data type.
 Keys must be immutable data type.

List
1.List operations
2.List slices
3.List methods
4.List loop
5.Mutability
6.Aliasing
7.Cloning lists
8.List parameters

List
Operations on list
1. Indexing
2. Slicing
3. Concatenation
4. Repetitions
5. Updating
6. Membership
7. Comparison

List
.
Operation Example Description
create a list
>>> a=[2,3,4,5,6,7,8,9,10]
>>> print(a)
[2, 3, 4, 5, 6, 7, 8, 9, 10]
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
Accessing the item in the
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]
Printing a part of the list.
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 list.
Updating
>>> print(a[2])
4
>>> a[2]=100
>>> print(a)
[2, 3, 100, 5, 6, 7, 8, 9, 10]
Updating the list using index
value.

List
List slices
List slicing is an operation that extracts a subset of elements from an
list.
Operation Example Description
Membership
>>> a=[2,3,4,5,6,7,8,9,10]
>>> 5 in a
True
>>> 100 in a
False
>>> 2 not in a
False
Returns True if element is
present in list. Otherwise returns
false.
Comparison
>>> a=[2,3,4,5,6,7,8,9,10]
>>>b=[2,3,4]
>>> a==b
False
>>> a!=b
True
Returns True if all elements in
both elements are same.
Otherwise returns false

List
Syntax
listname[start:stop]
listname[start:stop:steps]
 Default start value is 0
 Default stop value is n-1
 [:] this will print the entire list
 [2:2] this will create a empty slice slices example
Slices Example Description
a[0:3]
>>> a=[9,8,7,6,5,4]
>>> a[0:3]
[9, 8, 7]
Printing a part of a list from 0 to
2.
a[:4] >>> a[:4]
[9, 8, 7, 6]
Default start value is 0. so prints
from 0 to 3
a[1:] >>> a[1:]
[8, 7, 6, 5, 4]
Default stop value will be n-1. so
prints from 1 to 5

List
List methods
 Methods used in lists are used to manipulate the data quickly.
 These methods work only on lists.
 They do not work on the other sequence types that are not mutable,
that is, the values cannot be changed.
Syntax
list name.method name( element/index/list)
Slices Example Description
list.append(element)
>>> a=[1,2,3,4,5]
>>> a.append(6)
>>> print(a)
[1, 2, 3, 4, 5, 6]
Add an element to the end of the
list
list.insert(index,element
)
>>> a.insert(0,0)
>>> print(a)
[0, 1, 2, 3, 4, 5, 6]
Insert an item at the defined
index
min(list) >>> min(a)
2
Return the minimum element in a
list

List
. Syntax Example Description
list.extend(b)
>>> b=[7,8,9]
>>> a.extend(b)
>>> print(a)
[0, 1, 2, 3, 4, 5, 6, 7, 8,9]
Add all elements of a list to the
another list
list,index(element)
>>> a.index(8)
8
Returns the index of the element
list.sort()
>>> a.sort()
>>> print(a)
[0, 1, 2, 3, 4, 5, 6, 7, 8,9]
Sort items in a list
list.reverse()
>>> a.reverse()
>>> print(a)
[9,8, 7, 6, 5, 4, 3, 2, 1, 0]
Reverse the order.
list.remove(element)
>>> a.remove(0)
>>> print(a)
[9,8,7, 6, 5, 4, 3, 2,1]
Removes an item from the list
list.copy()
>>> b=a.copy()
>>> print(b)
[9,8,7, 6, 5, 4, 3, 2,1]
Copy from a to b
len(list)
>>>len(a)
9
Length of the list

List
Try yourself:
list.pop()
list.pop(index)
list.remove(element)
list.count(element)
max(list)
list.clear()
del(list)

List
List loops
1. for loop
2. while loop
3. infinite loop
for 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.
 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.
Syntax:
for variable in sequence:

List
Example
Accessing element
a=[10,20,30,40,50]
for i in a:
print(i)
Output
10
20
30
40
50
Accessing index output
a=[10,20,30,40,50]
for i in range(0,len(a),1):
print(i)
output
0
1
2
3
4
Accessing element using range
a=[10,20,30,40,50]
print(a[i])
----------------------------------------------------------
print(id(a[i])) # for memory address
output
10
20
30
40
50

List
While loop
 The while loop is used to iterate over a block of code as long as the
test condition is true.
 When the condition is tested and the result is false, the loop body
will be skipped and the first statement after the while loop will be
executed.
Syntax:
while (condition):
body of the statement
Example: Sum of the elements in
list
a=[1,2,3,4,5]
i=0
sum=0
while i<len(a):
sum=sum+a[i]
i=i+1
print(sum)
Output
15

List
infinite Loop
 A loop becomes infinite loop if the condition becomes false.
 It keeps on running. Such loops are called infinite loop.
Example:
a=1
while (a==1):
n=int(input("enter the number"))
print("you entered:" , n)
Output
Enter the number 10
you entered:10
Enter the number 12
you entered:12
Enter the number 16
you entered:16

List
Mutability
 Lists are mutable.(It can be changed)
 Mutability is the ability for certain types of data to be changed without
entirely recreating it.
 An item can be changed in a list by accessing it directly as part of the
assignment statement.
 Using the indexing operator on the left side of an assignment, one of
the list items can be updated.
 Example:
>>> a=[1,2,3,4,5]
>>> a[0]=100
>>> print(a)
[100, 2, 3, 4, 5]
changing single element
>>> a=[1,2,3,4,5]
>>> a[0:3]=[100,100,100]
>>> print(a)
[100, 100, 100, 4, 5]
changing multiple element

List
Aliasing(copying)
 Creating a copy of a list is called aliasing.
 When you create a copy both list will be having same memory location.
 Changes in one list will affect another list.
 Aliasing refers to having different names for same list values.
Example:
a= [1, 2, 3 ,4 ,5]
b=a
print (b)
a is b
a[0]=100
print(a)
print(b)
[1, 2, 3, 4, 5]
[100,2,3,4,5]
[100,2,3,4,5]

List
Cloning
 Creating a copy of a same list of elements with different memory
locations is called cloning.
 Changes in one list will not affect locations of another list.
 Cloning is a process of making a copy of the list without modifying the
original list.
1. Slicing
2. list()method
3. copy() method
Example:
cloning using Slicing
>>>a=[1,2,3,4,5]
>>>b=a[:]
>>>print(b)
[1,2,3,4,5]
>>>a is b
False

List
. clonning using list() method
>>>a=[1,2,3,4,5]
>>>b=list(a)
>>>print(b)
[1,2,3,4,5]
>>>a is b
false
>>>a[0]=100
>>>print(a)
>>>a=[100,2,3,4,5]
>>>print(b)
>>>b=[1,2,3,4,5]
clonning using copy() method
a=[1,2,3,4,5]
>>>b=a.copy()
>>> print(b)
[1, 2, 3, 4, 5]
>>> a is b
False

List
List as parameters
 Arguments are passed by reference.
 If any changes are done in the parameter, then the changes also
reflects back in the calling function.
 When a list to a function is passed, the function gets a reference to the
list.
 Passing a list as an argument actually passes a reference to the list, not
a copy of the list.
 Lists are mutable, changes made to the elements.
 Example
def remove(a):
a.remove(1)
a=[1,2,3,4,5]
remove(a)
print(a)
Output
[2,3,4,5]

List
. Example 2:
def inside(a):
a[i]=a[i]+10
print(“inner”,a)
a=[1,2,3,4,5]
inside(a)
print(“outer”,a)
output
inner [11, 12, 13, 14, 15]
outer [11, 12, 13, 14, 15]
Example3:
def insert(a):
a.insert(0,30)
a=[1,2,3,4,5]
insert(a)
print(a)
output
[30, 1, 2, 3, 4, 5]

List
Practice
1.list=[‘p’,’r’,’I’,’n’,’t’]
print list[-3:]
Ans:
Error, no parenthesis in print statement.
2.Listout built-in functions.
Ans:
max(3,4),min(3,4),len(“raj”),range(2,8,1),round(7.8),float(5),int(5.0)
3.List is mutable-Justify
Ans:
List is an ordered sequence of items. Values in the list are called elements/items.
List is mutable. i.e. Values can be changed.
a=[1,2,3,4,5,6,7,8,9,10]
a[2]=100
print(a) -> [1,2,100,4,5,6,7,8,9,10]

Advanced list processing
List Comprehension
 List comprehensions provide a brief way to apply operations on a list.
 It creates a new list in which each element is the result of applying a
given operation in a list.
 It consists of brackets containing an expression followed by a “for”
clause, then a list.
 The list comprehension always returns a result list.
Syntax
list=[ expression for item in list if conditional ]

Advanced list processing
.
List Comprehension output
>>>L=[x**2 for x in range(0,5)]
>>>print(L)
[0, 1, 4, 9, 16]
>>>[x for x in range(1,10) if x%2==0] [2, 4, 6, 8]
>>>[x for x in 'Python Programming' if x in
['a','e','i','o','u']]
['o', 'o', 'a', 'i']
>>>mixed=[1,2,"a",3,4.2]
>>> [x**2 for x in mixed if type(x)==int]
[1, 4, 9]
>>>[x+3 for x in [1,2,3]] [4, 5, 6]
>>> [x*x for x in range(5)] [0, 1, 4, 9, 16]
>>> num=[-1,2,-3,4,-5,6,-7]
>>> [x for x in num if x>=0]
[2, 4, 6]
>>> str=["this","is","an","example"]
>>> element=[word[0] for word in str]
>>> print(element)
['t', 'i', 'a', 'e']

Nested list
 List inside another list is called nested list.
Example
>>> a=[56,34,5,[34,57]]
>>> a[0]
56
>>> a[3]
[34, 57]
>>> a[3][0]
34
>>> a[3][1]
57

Tuple
 A tuple is same as list, except in parentheses instead of square
brackets.
 A tuple is an immutable list. i.e. can not be changed.
 Tuple can be converted into list and list can be converted in to tuple.
Benefit:
 Tuples are faster than lists.
 Tuple can be protected the data.
 Tuples can be used as keys in dictionaries, while lists can't.
Operations on Tuples:
1. Indexing
2. Slicing
3. Concatenation
4. Repetitions
5. Membership
6. Comparison

Tuple
 . Operations Example Description
Creating a tuple
>>>a=(20,40,60,”raj”,”man”) Creating the tuple with different
data types.
Indexing
>>>print(a[0])
20
Accessing the item in the position
0
Slicing
>>>print(a[1:3])
(40,60)
Displaying elements from 1st to
2nd.
Concatenation
>>> b=(2,4)
>>>print(a+b)
>>>(20,40,60,”raj”,”man”,2,4)
Adding tuple elements.
Repetition
>>>print(b*2)
>>>(2,4,2,4)
Repeating the tuple
Membership
>>> a=(2,3,4,5,6,7,8,9,10)
>>> 5 in a
True
>>> 2 not in a
False
If element is present in tuple
returns TRUE else FALSE
Comparison
>>> a=(2,3,4,5,6,7,8,9,10)
>>>b=(2,3,4)
>>> a==b
False
If all elements in both tuple same
display TRUE else FALSE

Tuple
Tuple methods
 Tuple is immutable. i.e. changes cannot be done on the elements of a
tuple once it is assigned.
Methods Example Description
tuple.index(element)
>>> a=(1,2,3,4,5)
>>> a.index(5)
4
Display the index number of
element.
tuple.count(element)
>>>a=(1,2,3,4,5)
>>> a.count(3)
1
Number of count of the given
element.
len(tuple)
>>> len(a)
5
The length of the tuple
min(tuple)
>>> min(a)
1
The minimum element in a tuple
max(tuple)
>>>max(a)
5
The maximum element in a tuple
del(tuple) >>>del(a) Delete the tuple.

Tuple
Convert tuple into list
Convert list into tuple
Methods
Example
Description
list(tuple)
>>>a=(1,2,3,4,5)
>>>a=list(a)
>>>print(a)
[1, 2, 3, 4, 5]
Convert the given tuple into
list.
Methods
Example
Description
tuple(list)
>>> a=[1,2,3,4,5]
>>> a=tuple(a)
>>> print(a)
(1, 2, 3, 4, 5)
Convert the given list into
tuple.

Tuple
Tuple Assignment
 Tuple assignment allows, variables on the left of an assignment operator and
values on the right of the assignment operator.
 Multiple assignment works by creating a tuple of expressions from the right
hand side, and a tuple of targets from the left, and then matching each
expression to a target.
 It is useful to swap the values of two variables.
Example:
Swapping using temporary variable Swapping using tuple assignment
a=20
b=50
temp=a
a=b
b=temp
print("value after swapping is",a,b)
a=20
b=50
(a,b)=(b,a)
print("value after swapping is",a,b)

Tuple
Multiple assignments
 Multiple values can be assigned to multiple variables using tuple
assignment.
Example
>>>(a,b,c)=(1,2,3)
>>>print(a)
1
>>>print(b)
2
>>>print(c)
3

Tuple
Tuple as return value
 A Tuple is a comma separated sequence of items.
 It is created with or without ( ).
 A function can return one value.
 if you want to return more than one value from a function then use tuple
as return value.
Example:
Program to find quotient and reminder output
def div(a,b):
r=a%b
q=a//b
return(r,q)
a=eval(input("enter a value:"))
b=eval(input("enter b value:"))
r,q=div(a,b)
print("reminder:",r)
print("quotient:",q)
enter a value:5
enter b value:4
reminder: 1
quotient: 1

Tuple
Tuple as argument
 The parameter name that begins with * gathers argument into a tuple.
Example
def printall(*args):
print(args)
printall(2,3,'a')
Output:
(2, 3, 'a')

Dictionaries
 Dictionary is an unordered collection of elements.
 An element in dictionary has a key:value pair.
 All elements in dictionary are placed inside the curly braces i.e. { }
 Elements in Dictionaries are accessed via keys.
 The values of a dictionary can be any data type.
 Keys must be immutable data type.
Operations on dictionary
1. Accessing an element
2. Update
3. Add element
4. Membership

Dictionaries
 . Operations Example Description
Creating a
dictionary
>>> a={1:"one",2:"two"}
>>> print(a)
{1: 'one', 2: 'two'}
Creating the dictionary with
different data types.
Accessing an
element
>>> a[1]
'one'
>>> a[0]
KeyError: 0
Accessing the elements by
using keys.
Update
>>> a[1]="ONE"
>>> print(a)
{1: 'ONE', 2: 'two'}
Assigning a new value to key.
Add element
>>> a[3]="three"
>>> print(a)
{1: 'ONE', 2: 'two', 3: 'three'}
Add new element in to the
dictionary with key.
Membership
a={1: 'ONE', 2: 'two', 3: 'three'}
>>> 1 in a
True
>>> 3 not in a
False
If the key is present in
dictionary returns TRUE else
FALSE

Dictionaries
Methods in dictionary
Method Example Description
Dictionary.copy()
a={1: 'ONE', 2: 'two', 3: 'three'}
>>> b=a.copy()
>>> print(b)
{1: 'ONE', 2: 'two', 3: 'three'}
copy dictionary ’a’ to
dictionary ‘b’
Dictionary.items()
>>> a.items()
dict_items([(1, 'ONE'), (2,
'two'), (3, 'three')])
It displays a list of
dictionary’s (key, value) tuple
pairs.
Dictionary.key() >>> a.keys()
dict_keys([1, 2, 3])
Displays list of keys in a
dictionary.
Dictionary.values()
>>> a.values()
dict_values(['ONE', 'two',
'three'])
Displays list of values in a
dictionary.
Dictionary.pop(key
)
>>> a.pop(3)
'three'
>>> print(a)
{1: 'ONE', 2: 'two'}
Remove the element with
key.

Dictionaries
Try yourself
Dictionary.setdefault(key,value)
Dictionary.update(dictionary)
Dictionary.fromkeys(key,value)
len(Dictionary name)
Dictionary.clear()
del(Dictionary name)

Comparison of List, Tuples and Dictionary
. List Tuple Dictionary
A list is mutable A tuple is immutable A dictionary is mutable
Lists are dynamic Tuples are static Values can be of any
data type and can
repeat.
Keys must be of
immutable type
Homogenous Heterogeneous Homogenous
Slicing can be done Slicing can be done Slicing can't be done

Assignment
1.Addition of matrix
2.Multiplication of matrix
3.Transpose of matrix
4.Selection sort
5.Insertion sort
6.Merge sort
7.Histogram
email:mrajen@rediffmail.com

Python for Beginners(v3)

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