List and Scope

List and scope

Whta is Data structure ?

ans: Providing structure to the data is called data structure.

print the whole list

 
    arr = [5, 12,"Tajmahal",45.77,True,"Tajmahal"]
    print(arr)
 
    output:
    [5, 12, 'Tajmahal', 45.77, True, 'Tajmahal'] 

print the length of index

 
    arr = [5, 12,"Tajmahal",45.77,True,"Tajmahal"]
    print(len(arr))
 
    output: 6

Access 2 and 5 index

 
    arr = [5, 12,"Tajmahal",45.77,True,"Tajmahal"]
    print(arr[2], arr[5])
 
    output: Tajmahal Tajmahal

Check the data type of "arr"

 
    arr = [5, 12,"Tajmahal",45.77,True,"Tajmahal"] 
    print(type(arr))
     
    OUTPUT: <class 'list'>

Create an empty list

 
    empty = []
    print(empty)

Another way to create an empty list.

    ## Another way to create an empty list.
    list_name = list()   # This is also a empty list.
 

Slicing

 
    slr = [2, 5, 7, 8,2,100,"Angela Yu","London",43.55]
    print(slr[2], slr[3])
 
    output: 7 8

Print whole list using range function

 
    slr = [2, 5, 7, 8,2,100,"Angela Yu","London",43.55]
     for i in slr:
        print(i,end = " ")
     
    output: 2 5 7 8 2 100 Angela Yu London 43.55

Print 2 to 9 elements from slr list

 
    slr = [2, 5, 7, 8,2,100,"Angela Yu","London",43.55]
     
    print(slr[2:9])
 
    OUTPUT:  [7, 8, 2, 100, 'Angela Yu', 'London', 43.55]

HOW IT WORKING UNDERSTAND

 
    slr = [2, 5, 7, 8,2,100,"Angela Yu","London",43.55]
    print(slr[1:10:2])
 
    OUTPUT: [5, 8, 100, 'London']

print(slr[1:10:2])

1 is a starting number

10 is an ending number

2 is a step size

print elements which are on even index.

     
    lst = [2,3,5,6,7,8,96,42,35,21,234,554,433]
 
     
    for i in range(len(lst)):
        if i % 2 == 0:
            print(lst[i])
 
 
    output:
    2
    5
    7
    96
    35
    234
    433 

 
 

Another list example:

 
 names = ["Angela","Elon Musk","Jarvis","Linux","Telegram","python"]

    for indx in range(5):
        print("Hello", names[indx])
 
    OUTPUT: 
 
    Hello Angela Yu
    Hello Elon Musk
    Hello Jarvis
    Hello Linux
    Hello Telegram

MCQ 1

 
    lst = [1,2,3,4,5,6,7,8,9,10]
    print(lst[0:len(lst):2])

    # output: 1,3,5,7,9

0 is a starting number

len(lst) is 10

2 is a step size.

print(lst[0:10:2])

MCQ: 2

 
    a = [1,2,3,4]
    print(a[len(a)-1:0:-1 ])

    ## len(a)-1 = 3         (a[3:0:-1])
 
    output: [4, 3, 2]

It will print whole list

 
    a = [1,2,3,4]
    print(a[0:len(a):1])
 
     OUTPUT: [1, 2, 3, 4]

MCQ:3

    aa = [1,2,3,4,5]
    aa.append(15)
    print(aa[-1])

    # output: 15
 

MCQ: 4

 
    i = [1,2,3,4]
    i.insert(2,15)
    print(i[2])

    # output: 15

Append function

 
    box = [3,4,5,6,7,9]

    # Adding an elements to the end using append function.
    # append does not want index 
    box.append("Linux Debian")    print(box)
 
    output: [3, 4, 5, 6, 7, 9, 'Linux Debian']

Insert function

 
    box = [3,4,5,6,7,9]
    box.insert(4, "Dream not sleep")
    print(box)
 
    output:  [3, 4, 5, 6, 'Dream not sleep', 7, 9]

Negative indexing

 
    py = [1,2,3,4,5,6,78,9] 
    print(py[-1]) # output: 9
    print(py[-3]) # output: 6
    print(py[-2]) # output: 78
 

Others

    py = [1,2,3,4,5,6,78,9] 

    # it will print from 0 to 6
    print(py[:6]) # same as print(py[0:6])

    # it will print from 2s and go till the end.
    print(py[2:])  # same as print(py[2:8])

    # it will print whole the elements (start from beginning and go till the end)
    print(py[:]) # same as print(py[0:8])

    # step size is 2
    print(py[::2])  
 
    # output: [1, 3, 5, 78]
 
    # it will start from beginning and go to -1 
    print(py[:-1]) 
     
     # output: [1, 2, 3, 4, 5, 6, 78]

    # reversing the list
    print(py[::-1])   
 
    # output: [9, 78, 6, 5, 4, 3, 2, 1]