How to Iterate Over a List and Get Indexes with 'enumerate' Function in Python

'enumerate' function

There are different ways of accessing the data from a list like using range and then index or accessing the element of a list directly from for loop and so on. 

One other powerful way is by using 'enumerate' function. One major advantage of using 'enumerate' is this function returns both index and corresponding element at once. So, we don't have to maintain a counter to calculate the index or need to retrieve the element from a index. This makes the code easy to maintain and understand. 

In this post, we will see how to use 'enumerate' function and looping over a list to access index and elements as a tuple and also by using tuple unpacking. 

Syntax

enumerate(iterable, start=0)

'enumerate' function accepts two parameters. 

• 'iterable' - This is a mandatory parameter. An iterable (E.g.: list, tuple, string...) on which we need to run the loop and retrieve index and element.
• 'start' - This is an optional parameter. 'start' specifies the number of the first index (This works more like a counter than index). Default value is '0'. 

Let's have a look at an example for looping over a list using enumerate. 

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fruits = ['apple', 'banana', 'cherry'] for index, fruit in enumerate(fruits):    print(index, fruit)

In the above example, we are only passing the list to the enumerate function, so start index would be considered as '0' and returns the index and element combination for every iteration. Below is the result. 

0 apple 1 banana 2 cherry

Let's have another example by passing an optional parameter 'start'. 

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fruits = ['apple', 'banana', 'cherry'] for index, fruit in enumerate(fruits, 1):    print(index, fruit)

In the above example, we are passing '1' as the start. One thing to here is, it is not like slicing where the loop is iterated from the index passed for 'start'. Instead, enumerate start indexing from '1'. It is better understood by looking at the result. 

1 apple 2 banana 3 cherry

This can be useful in the cases where we need to start numbering from '1' (or any other number instead of zero) and continue till the end of the list. 

In the above examples, we are directly unpacking the tuple from 'enumerate' function as index and fruit. 

We can also use it as a tuple instead. 

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fruits = ['apple', 'banana', 'cherry'] for fruit_tuple in enumerate(fruits, 1):    print(fruit_tuple)

Unlike previous examples, we are not using two different variables (for index and element) in for loop, instead we are only passing one variable. In this case, index and element combination is returned as a tuple. Below is the result.

(1, 'apple') (2, 'banana') (3, 'cherry')

As we have seen in the above examples, we can loop over an iterator with index and element combination as a tuple or directly assigning to two different variables as required in the loop and either to start the counter from default '0' or by specifying the required start position. 

I hope this post has provided a good insight on how to iterate over a list and get index and element from an iterator using 'enumerate' function.

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