Deep in Python list

 

Most Important in Python(0-Z)

1.What is List. Explain in Detail

         The list class is a fundamental built-in data type in Python        

Ø  Ordered: They contain elements or items that are sequentially arranged according to their specific insertion order.

Ø  Zero-based: They allow you to access their elements by indices that start from zero.

Ø  Mutable: They support in-place mutations or changes to their contained elements.

Ø  Heterogeneous: They can store objects of different types.

Ø  Growable and dynamic: They can grow or shrink dynamically, which means that they support the addition, insertion, and removal of elements.

Ø  Nestable: They can contain other lists, so you can have lists of lists.

Ø  Iterable: They support iteration, so you can traverse them using a loop or comprehension while you perform operations on each of their elements.

Ø  Sliceable: They support slicing operations, meaning that you can extract a series of elements from them.

Ø  Combinable: They support concatenation operations, so you can combine two or more lists using the concatenation operators.

In Python, lists are ordered, which means that they keep their elements in the order of insertion

 

Ex: a = [1, 2, 3, 4]

         shopping = ["Milk", "Eggs", "Bread"]

         list_name = [item1, item2, item3]

List is Mutable (VERY IMPORTANT)

👉 You can modify list after creation

Ex:-

Indexing (in List Access Elements):-

You can access an individual object in a list by its position or index in the sequence. Indices start from zero:

Synatx :list_object[index]

           Ex:list[0] – acess First Element in List

 

Type in Command Each below:-

course=["P","Y","T","H","O","N"]
print(course)
#Access First element in List
print("Access First element in List",course[0])
#Access last element in List
print("Access last element in List",course[-1])
#Above statement i don't know string elements that y use this one
print("Access last element in List",course[5])
#Above statement i  know string elements that y use this one
print("Access last using len function element in List",course[len(course)-1])
#aceess First two elements from list
print("Access last element in List",course[0,1]) --error Beasuce Index not work

Slicling:-

Retrieving Multiple Items From a List: Slicing

Syntax:- list_object[start:stop:step]

The [start:stop:step] part of this construct is known as the slicing operator. Its syntax consists of a pair of square brackets and three optional indices, start, stop, and step. The second colon is optional. You typically use it only in those cases where you need a step value different from 1.

• start specifies the index at which you want to start the slicing. The resulting slice includes the item at this index.
• stop specifies the index at which you want the slicing to stop extracting items. The resulting slice doesn’t include the item at this index.
• step provides an integer value representing how many items the slicing will skip on each step. The resulting slice won’t include the skipped items.

                                  Index                           Default Value

                                  start                                    0

                                  stop                         len(list_object)

                                  step                                       1

Example:

letters = ["A", "a", "B", "b", "C", "c", "D", "d"]

I want Upper case letter From List

Index start with hear à0

Stop hear d(Means 8)

Step 2 counter

upper_letters = letters[0::2] –smart way

letters = ["A", "a", "B", "b", "C", "c", "D", "d"]
uppercase=letters[0:8:2]  --Understanding Way this also give same result
print(uppercase)

 

Home work Lower Case you Can try :

 

Pro Level:-

digits = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
#0 to 5 from list
print(digits[0:4]) # Res [0, 1, 2, 3]
print(digits[:4])  # Res [0, 1, 2, 3]
print(digits[-4:]) #res [6, 7, 8, 9]
print(digits[0:len(digits):2]) #res [0, 2, 4, 6, 8]
course=["P","Y","T","H","O","N"]
print(course[::-1]) # res ['N', 'O', 'H', 'T', 'Y', 'P']--revse String

To change the value of a given element in a list, you can use the following syntax:

list_object[index] = new_value

 

In Python, you’ll have two kinds of mechanisms to create copies of an existing list. You can create either:

1.   A shallow copy

2.   A deep copy

Both types of copies have specific characteristics that will directly impact their behaviour. In the following sections, you’ll learn how to create shallow and deep copies of existing lists in Python. First, you’ll take a glance at aliases, a related concept that can cause some confusion and lead to issues and bugs.

Methods in list:

List Methods

Let's look at different list methods in Python:

• append(): Adds an element to the end of the list.

Syntax: list_name.append(element)

• copy(): Returns a shallow copy of the list.

         Syntax: list_name.copy()

• clear(): Removes all elements from the list.

Syntax: list_name.clear()

• count(): Returns the number of times a specified element appears in the list.

         Syntax: list_name.count(element)

• extend(): Adds elements from another list to the end of the current list.

         Syntax: list_name.extend(iterable)

• index(): Returns the index of the first occurrence of a specified element.

Syntax: list_name.index(element)

• insert(): Inserts an element at a specified position.

         Syntax: list_name.insert(index, element)

• pop(): Removes and returns the element at the specified position (or the last element if no index is specified).

Syntax: list_name.pop(index)

• remove(): Removes the first occurrence of a specified element.

Syntax: list_name.remove(element)

• reverse(): Reverses the order of the elements in the list.

         Syntax: list_name.reverse()

• sort(): Sorts the list in ascending order (by default).

Syntax: list_name.sort(key=None, reverse=False)

 

 

Max , Min,and there or more find your self map filter alos those this  your home work

 

 

 

 

 

 

 

 

 

 

Python list Interview Q&A

 #----------------List Interview Question For Zero to Adv Level--------

# Reverse a list

number=[10,30,20,40,60,90,80,100]

# using sort and reverse keyword we can use

number.sort(reverse=True)

print(number) # result [100, 90, 80, 60, 40, 30, 20, 10]

number1=[10,30,20,40,60,90,80,100]

#without Sort and reverse key word

print(number1[::-1]) #result [100, 80, 90, 60, 40, 20, 30, 10]

#2. Find largest & smallest

number2=[10,30,20,40,60,90,80,100]

print(max(number2)) # Max Number is 100

print(min(number2)) # Min Number is 10

print(sum(number2)) # Sum of Number is 430

#3.Count occurrences

number2=[10,30,20,40,20,20,20,60,90,80,100]

print(number2.count(20)) # Result is 4

#4.Remove duplicates

print(list(set(number2))) #[100, 40, 10, 80, 20, 90, 60, 30]

#5 Second_largest number in list

L1=list(set(number2)) # Remove Duplicates

L1.sort() # sort the List

print(L1[-2]) # Find the Second_Highest Number

mylist = ['apple', 'banana', 'cherry']

mylist[1:2] = ['kiwi', 'mango']

print(mylist) 

print(mylist[2])

Python List Full Infromation with Interview questions

 #LIST --List one of the data type in python

#A List is a collection of items stored in a single variable.

#list can store multiple values with comma speciation

#list we can identify  begins with an opening square bracket and

#ends with a closing square bracket, []

#A list value looks like this: ['cat', 'bat', 'rat', 'elephant'].

# list is Ordered,Mutable (changeable),Allow duplicates ,Can store different data types

#

animals=["cat","rat","Cow","Hen","horse","dog"]

print("Name of the animals Is",animals)

#in List data type we can store String values ,Int values ,flote values anything

animals_digits=["cat","0","rat","1","Cow","2","Hen","3","horse","4","dog","5"]

print("Name of the animals Is",animals_digits)

#Just as an index can get a single value from a list,

#List value Index --> it will Index first value from list

print(animals_digits[0])

print(animals_digits[1]) #it will Index 2 value from list

print(animals_digits[2]) #it will Index 3 value from list

print(animals_digits[-1]) #it will Negative Index Last value from list

print(animals_digits[-2])

#a slice can get several values from a list, in the form of a new list

print(animals_digits[0:4]) # Get 0,1,2,3 values from List # means 0-cat,1-0,2-rat,3-1

text = "HELLO"

print(text[1])     # E

print(text[1:2])   # E (but type is different!)

text = "PYTHON"

print(text[::2]) # Result is PTO Means Step = 2 (skip one)

Blak = "Mahen"

print(Blak[1:10])

#-------------------------------------------------

text = "HELLO"

print(text[1:2] == text[1]) # Result should be True

# Both are 'E', but types conceptually differ (still equal)

#---------------------------------------------------

nums = [10, 20, 30, 40]

print(nums[-3:-1])

#While Slicing start included, stop excluded

#Changing the Values in List

nums[0]=200 # Old Nums [10, 20, 30, 40]

print(nums) #Result should be [200, 20, 30, 40]

#List Concatenation(+) and List Replication(*)

value=[1, 2, 3] + ['A', 'B', 'C']

print(value) # Result is:-[1, 2, 3, 'A', 'B', 'C']

value=[1,2,3]*2

print(value) # Result  Is:[1, 2, 3, 1, 2, 3]

#Removing Values from Lists with del Statements

del value[1] # Result  Is:[1, 2, 3, 1, 2, 3]

print(value) #Result [1, 3, 1, 2, 3]

#Adding Values to Lists with the append() and insert() Methods

# sy : string.append(value)

s1=[1,2,3,'python','java']

s1.append('C++')

print(s1) #[1, 2, 3, 'python', 'java', 'C++']

#Insert Method SY: Insert(index,object)

str=[1,2,3,'python','java']

str.insert(2,'C') #[1, 2, 'C', 3, 'python', 'java']

print(str)

#Removing Values from Lists with remove()

str1=[1,2,3,'python','java']

str1.remove(2)

print(str1) # result [1, 3, 'python', 'java']

#Sorting the Values in a List with the sort() Method

str2=[0,5,13,9,6,20,15]

str2.sort() # result [0, 5, 6, 9, 13, 15, 20]

print(str2)

str2.sort(reverse=True) # result [20, 15, 13, 9, 6, 5, 0]

print(str2)

str3=[1, 3, 2, 4, 'Alice', 'Bob']

#str3.sort()

print(str3) #TypeError: '<' not supported between instances of 'str' and 'int'

#A list value is a mutable data type: It can have values added, removed, or changed.

#List Copy

l1=str1.copy() #str1 copy into l1

print(l1)

#========== real Time Interview question ===============

#Find the largest Number in given LIST

Numbers=[10,20,30,50,60] # Largest Number is 60

print(max(Numbers))  #->60

#Find the second-largest number in List

Numbers=[10,20,70,50,90,15,20,80,20,25,100]

Numbers.sort(reverse=False)

print(Numbers[-2])  # result 90

# Remove Duplicates in Given List

Number1=[10,20,70,50,90,15,20,80,20,25,100]

unique=list(set(Number1))

print(unique) #-->[100, 70, 10, 15, 80, 50, 20, 25, 90]

# List Unpacking

a, b, c = [10, 20, 30]

print(a, b, c) #

print(a+b)

print(a)

#Reveses list Using Reverse keyword without using reverse key word

nums = [1,2,3,4]

nums.sort(reverse=True)

print(nums)

print(nums[::1])#-Result [4, 3, 2, 1]

Even and Odd Value Find in python along examption handling

try:

    number = int(input("Enter a number: "))

    if number % 2 == 0:

        print("Even")

    else:

        print("Odd")

except ValueError:

    print("Invalid input! Please enter a valid number.") 

Funtion in Python

 #Input Function  waits for the user to type some text on the keyboard

myname=input("Enter your Name :")

print("Hello ,My Name is ", myname)

#len() length Function Find the Number Words given String out Put Should Be Integer

#Example len(Python)---> Python having 6 Charters

print("Length of Python Is ",len("python"))

# integer to String Convertion in Python

value ='I have eaten ' + str(99) + ' burritos.'

print(value)

#string to integer convertion in Python

value="99"

print(1+int(value))

#The == operator (equal to) asks whether two values are the same as each

#other.

#The = operator (assignment) puts the value on the right into the variable

#on the left.

ZERO to Hero Level Print Function Details in Python

# print Function in Python its   built-in    functions
#Print Function Display the result in Console/screen to user
#print function having multiple parameter
#---------Jut Print Hello world use Below Statement--
print("Hello World ")
#Printing Multiple Values
a=10
b=20
print(a+b)    # add two Numbers with sum
print(a , b ) # add Space to the values
# if u want Space in Each Value Using Seprator parameter In Print Function

print("Python", "Java", "C++", sep=" ** ")

#end Parameter Will Work Wat u need put end of statement

print("Python", "Java", "C++", sep=" ** ",end=" etc ....!")

#Flash value should true or false(It forces immediate output.) below \n means print result in new line

print("\n","Python", "Java", "C++", sep="%",end=" etc ....!",flush=False)
print("\n","Python", "Java", "C++", sep=" --",end=" etc ....!",flush=True)

#\t means new tab and \\ means Backslash \" menas Double quote

print("Hello\tworld", "hello\\world", "hello \" world")

#Syntax:print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

#objects    values to print sep    separator end  line ending file   output location

#flush  force output

 END ZERO to Hero Level Print Function Details in Python

Scinario Based interview Question .....

 How To Achieve The Scenario.

Input

File1.csv 

id,Name

1,Mahendra

File2.csv

City, State

Hyd,Telangana

File3.csv

Stateid

Ts

I want Out put

File.Csv

Id,Name,City,State,StateId

1,Mahendra,Hyd,telangana,Ts

Solution:-

[tFileInputDelimited (File1)] --> [tAddRowNumber] -->|

                                                      |

[tFileInputDelimited (File2)] --> [tAddRowNumber] -->|--> [tMap] --> [tFileOutputDelimited (File.csv)]

                                                      |

[tFileInputDelimited (File3)] --> [tAddRowNumber] -->|