How To Find Index Of Value In List Python

Python – Find Index or Position of Element in a List

To find index of the starting time occurrence of an element in a given Python List, yous can utilize index() method of List class with the element passed as argument.

            alphabetize = mylist.alphabetize(element)

The alphabetize() method returns an integer that represents the index of first match of specified element in the Listing.

You can also provide beginning and terminate positions of the List, where the search has to happen in the list.

Following is the syntax of index() function with kickoff and end positions.

            index = mylist.index(x, [start[,end]])

start parameter is optional. If y'all provide a value for start, then end is optional.

We shall expect into examples, where we go through each of these scenarios in detail.

Python - Index or Position of Specific Element in a List

Case 1: Discover Index of item in List

In the following example, nosotros have taken a List with numbers. Using index() method we will find the index of item eight in the list.

Python Programme

            mylist = [21, v, 8, 52, 21, 87] item = eight  #search for the particular alphabetize = mylist.index(item)  print('The index of', item, 'in the listing is:', index)

Run

Output

            The index of 8 in the list is: ii

The element is present at 3rd position, so mylist.alphabetize() role returned ii.

Instance ii: Observe Index of Detail in Listing – beginning, end

In the following example, nosotros take taken a Listing with numbers. Using alphabetize() method nosotros will detect the index of item 8 in the list. Besides, nosotros shall laissez passer offset and end. index() office considers only those elements in the list starting from start index, till stop position in mylist.

Python Programme

            mylist = [21, 8, 67, 52, 8, 21, 87] particular = eight showtime=2 stop=vii  #search for the item index = mylist.alphabetize(detail, start, finish)  impress('The index of', item, 'in the list is:', alphabetize)

Run

Output

            The index of 8 in the list is: four

Caption

            mylist = [21, viii, 67, 52, 8, 21, 87]                  ----------------- merely this part of the list is considered                          ^ index finds the element hither           0   1   2   3  4 => iv is returned by index()

Instance 3: Notice Index of Item – Particular has multiple occurrences in List

A Python Listing can contain multiple occurrences of an element. In such cases, only the index of first occurrence of specified element in the listing is returned.

Python Program

            mylist = [21, five, 8, 52, 21, 87, 52] item = 52  #search for the item alphabetize = mylist.alphabetize(item)  print('The alphabetize of', item, 'in the listing is:', index)

Run

Output

            The index of 52 in the list is: 3

The element 52 is nowadays two times, but only the index of first occurrence is returned by index() method.

Permit united states empathise how index() method works. The function scans the listing from starting. When the item matches the argument, the function returns that index. The later occurrences are ignored.

Instance 4: Find Index of Particular in List – Item not present

If the element that nosotros are searching in the List is non nowadays, you will go a ValueError with the message item is not in list.

In the following program, we have taken a list and shall attempt to find the index of an element that is non present in the listing.

Python Program

            mylist = [21, v, 8, 52, 21, 87, 52] item = 67  #search for the detail/element index = mylist.index(item)  impress('The alphabetize of', particular, 'in the list is:', alphabetize)

Run

Output

            Traceback (most recent call last):   File "instance.py", line 5, in <module>     alphabetize = mylist.index(item) ValueError: 67 is non in list

As alphabetize() tin can throw ValueError, use Python Try-Except while using index(). In the following example, we shall learn how to utilise try-except statement to handle this ValueError.

Python Program

            mylist = [21, 5, 8, 52, 21, 87, 52] item = 67  try: 	#search for the detail 	index = mylist.index(particular) 	impress('The index of', item, 'in the listing is:', index) except ValueError: 	impress('item not present')

Run

Output

            particular non present

The item, whose index nosotros are trying to notice, is not present in the list. Therefore, mylist.index(detail) throws ValueError. except ValueError: block catches this Mistake and the corresponding block is executed.