# 
#  Overview
**[`Itertools`](https://www.educative.io/answers/what-are-itertools-in-python)** is a module in Python that enables fast, and memory-efficient iteration over iterable data structures. 

The module has a number of functions that construct and return iterators. One such function is the **`zip_longest`** function. This function makes an iterator that aggregates elements from each of the iterables. The iteration continues until the longest iterable is not exhausted.

##
## Syntax

```py
zip_longest(*iterables, fillvalue=None)
```
This function takes two arguments: 

* **`iterables`**: This is the data structure(s) over which we want to iterate. 

* **`fillvalue`**: This is the value that we want to fill in the case where `iterables` are of uneven length. 

## Return value

The function returns the aggregated data structure.

## Example









 

import itertools


x =[1, 2, 3, 4, 5, 6, 7]
y =[8, 9, 10]
a = [12,13,14]
z = list(itertools.zip_longest(x, y, a, fillvalue = 'a'))
print("Aggregated List:",z)

# 
## Explanation
* **Lines 4–6**: We create three lists `x`, `y`, and  `a`. The longest list is `x`, because it contains the most number of elements.
- **Line 7**: We call the `zip_longest` function, which aggregates each item in the provided lists. We also provide the `fillvalue` as `a`. 

The output list shows the aggregated list where the missing values in the smaller lists are filled with `a`.

What is the itertools.zip_longest module in Python?

Itertools' zip_longest function in Python aggregates elements from input iterables until the longest one is exhausted, filling missing values with a specified fillvalue.