Python iterate list with index

In this post, you will learn different ways to iterate a list with index.

A list is a sequence of indexed and ordered values, like a dynamic size array. So that we can store multiple items in a single variable. It is mutable, which means we can change the order of elements in a list. It contains a list of any type of data object with a comma separated and enclosed within a square bracket. The elements in a list are indexed, the first item has an index [0], the second item has index [1] etc. In the development process, we may come to the situation where we need to loop through the list with the index. There are various ways to loop through a list. Here, we have mentioned most of them with a simple example -

Python iterate list using for loop with enumerate type

Python enumerate() function can be utilized to repeat the list in an enhanced way. This method adds a counter to an iterable and returns it (the enumerate object). It makes it simpler to monitor the substance of an iterable article. Subsequently, it diminishes the overhead of keeping a check of the components while the iteration operation.

list_elems = ['chair', 'fan', 'bulb', 'table', 'cooler']

# Iterate over the list
for index,value in enumerate(list_elems):
   print((index, value), end=' ')

(0, 'chair') (1, 'fan') (2, 'bulb') (3, 'table') (4, 'cooler')

Python iterate list using range() function

We can also use the combination of range() and len() functions to iterate a list with index.

list_elems = ['bread', 'cookies', 'chocolate', 'tea', 'cake']

# getting length of list
length = len(list_elems )
  
# Iterating the index
# same as 'for i in range(len(list_elems))'
for i in range(length):
    print((i, list_elems [i]), end=' ')

(0, 'bread') (1, 'cookies') (2, 'chocolate') (3, 'tea') (4, 'cake')

Python iterate list using zip() function

Python's zip() function makes an iterator that will aggregate elements from at least two iterables. It returns a zip object, which is an iterator of tuples where the main thing in each passed iterator is matched together, and afterward the second thing in each passed iterator is combined together and so on.

list1 = ['Biscuit', 'Chocolate', 'Cookies', 'Coffey']

for x in zip(range(len(list1)), list1):
        print(x)

(0, 'Biscuit')
(1, 'Chocolate')
(2, 'Cookies')
(3, 'Coffey')

Python iterate list using map() function

The map() function applies a function to each item of an iterable list and returns a list of the results. Lambda is an anonymous function that contains any number of arguments, but only one expression. Here, we have used both map() and lambda function to iterate over the list with index.

list_elems = [42, 74, 22, 65, 23, 52]

result = map(lambda x: (x, list_elems[x]), range(len(list_elems)))
 
print(list(result)) 

[(0, 42), (1, 74), (2, 22), (3, 65), (4, 23), (5, 52)]

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