Index in Python

 

Generally, we add elements in lists, tuples and we delete items, insert elements etc but how can we do that, how can we access a particular element, this is done by using index number.

PDF FOR INDEX IN PYTHON 

Ø  Index numbers are nothing but numbers which are given to elements in a list or tuple or array etc to access them.

Ø  Index number starts with zero and ends with one less than the given number but

For example

 List = [1,5,8,13,24,31]

0  1  2  3   4   5

Ø  Each index refers to one element, as we know here the elements in the list are 6 but the maximum index will be 5 this is because index starts with zero so maximum index will always be one less than the length of list or tuple or array etc.

ADVANTAGES in Python:

Ø  It makes our work easier like we can easily delete the element we want to delete by just using its index number.

Ø  There are lot of ways to print elements using index values.

Ø  By directly using that element in square brackets

For example: Python_closet = [7,27,56,65,48]   

0   1    2   3    4

If we want to print only one element of the list then we can print using its index number in square brackets like this

 Print(python_closet[3])   // here index 3 refers to the 4^th element in the list//

 65  

Syntax = print(list name or tuple name [index number])

 Here we printed pythoncloset[3]for the 4^th element in list because as we all know that index value starts with zero so for 4^th element in list its index will be one less than it 

EX: if we want to print second element then print(python_closet[1])

 If we want to print third element then print(python_closet[2]) like this we can use index number .

If in case we have a nested list or a nested tuple then we can access elements like this:

Python_closet=[2,36,56,[1,4,6,7]]

Here how can we take indexes for this nested list that will be your question, well it’s so simple.

Here the complete nested list will be considered as an index like

                                0, 1  2 , 3

     [2, 36, 54, [1 ,4, 6, 7]]

       0,  1 ,   2 ,    --- 3 ---

 If we want to print 6 from the above list

 Then print(python_closet[3][2])

6

Same for number 7  print(python_closet[3][3])

 7

This is because whole second list is a list and, in that list, again we take index values from zero, so if we want a number then bracket of index number of that list (to access elements inside that list), index of the element in that list. This might be somewhat confusing but when u try this on your IDE you will understand.     this is the method for nested ones

*** Accessing elements using negative indexes

We can also access elements using negative indexes like -1 and -2

For example:mypython = [31,65,69,72,84]

 -5 , -4 , -3,-2 ,-1

Here in negative indexes the last number of the list or the index of the last element of list will be -1, as we know indexes start from zero but if we want to use negative index then last element will always have an index of -1 and then it comes in reverse -2 ,-3 and so on

Example:  print(mypython[-1])

                    84

                  Print(mypython[-3])

                  69

*** Accessing elements using slicing

              Pythontuple=(25, 36 ,42 ,79 ,51)

 0 , 1 ,   2 ,  3 ,   4

Ø   using ":" this operator we can print from one particular element to another element.

     

print(pythontuple[0:3])

 

so from the first index to the second index we give it will print all the elements in between that two indexes including first index but it will exclude last index that means in above case it starts printing from index 0 to 2 but it will not print the element in 3^rd index which means here the last element

 

 example:  print(pythontuple[0:3])  3^rd index will be excluded and till 2^nd index elements will be printed

                     25 , 36, 42

                     print(pythontuple[2:4])

                      42 ,

 4^th index will be excluded because it is the element given after colon or the last index, it prints from 2^nd index and 3^rd index and it stops.

 

Ø  If we don’t define any index value before operator then it automatically takes the first

           Element

Example:  print(pythontuple[:3])

 25 , 36 , 42

Here we didn’t mention an index before colon which means I didn’t give any  index number from which index the elements should be printed ,  when we don’t mention any index before colon then computer will automatically consider 0 which means here 0 index so from there it starts printing elements , if we want to print elements from first index then we need not mention zero it will automatically consider zero if we don’t write any number.

What happens if we don’t give last index, I mean what happens when we don’t mention any number after colon

 Example:  print(pythontuple[2:])

Here we didn’t give the last index or index after colon so what happens is it will print till the last element in that tuple

 Print(pythontuple[2:])

42,79,51

So here it prints till last element

What happens if we don’t give both the numbers, which means what happens when we don’t mention the index before colon and after the colon also

Then it prints all the values from first element to last element in that tuple Including first and last element also. so, if you want to print that complete tuple just put: this symbol and print

       Print(pythontuple[:])

       25 ,35 ,42 ,79 ,51

Ø  This is what happens because if we don’t define any index value before the symbol it automatically takes 0 as first index and if we don’t mention any index after symbol it prints till the last element. so, if we don’t give both then all elements in that list or tuple will be printed.

   

**** programming is not about reading some books or remembering some functions ,it is about practicing the more you do the more you will get so just don’t read and stop ,read and try to do code so that u can remember stuff and can understand still better when you try TO DO  them on your  IDE.

YOU CAN DOWNLOAD PDF HERE INDEX IN PYTHON  

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