# Python | Convert Triple nesting to Double nesting list

• Last Updated : 28 Aug, 2019

Sometimes, while working with lists, we can have a problem in which we need to perform the flattening of nested list. This kind of problem have been discussed many times. But sometimes, flattening can be from a triple to double nesting as well. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using list comprehension
This task can be performed using technique of list comprehension. In this, one can just take the initial element of triple nested list and just unpack it to double nested list.

 `# Python3 code to demonstrate working of``# Convert Triple nesting to Double nesting list``# using list comprehension`` ` `# initialize list``test_list ``=` `[[[``1``, ``4``, ``6``]], [[``8``, ``9``, ``10``, ``7``]]]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Convert Triple nesting to Double nesting list``# using list comprehension``res ``=` `[sub[``0``] ``for` `sub ``in` `test_list]`` ` `# printing result``print``(``"Double nested list from triple nested : "` `+` `str``(res))`

Output :

```The original list is : [[[1, 4, 6]], [[8, 9, 10, 7]]]
Double nested list from triple nested : [[1, 4, 6], [8, 9, 10, 7]]
```

Method #2 : Using `chain.from_iterable()`
This task can also be performed using this function. This is the inbuilt method that is made to perform the task of flattening a list and hence is highly recommended to perform this task.

 `# Python3 code to demonstrate working of``# Convert Triple nesting to Double nesting list``# using chain.from_iterable()``from` `itertools ``import` `chain`` ` `# initialize list``test_list ``=` `[[[``1``, ``4``, ``6``]], [[``8``, ``9``, ``10``, ``7``]]]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Convert Triple nesting to Double nesting list``# using list comprehension``res ``=` `list``(chain.from_iterable(test_list))`` ` `# printing result``print``(``"Double nested list from triple nested : "` `+` `str``(res))`

Output :

```The original list is : [[[1, 4, 6]], [[8, 9, 10, 7]]]
Double nested list from triple nested : [[1, 4, 6], [8, 9, 10, 7]]
```

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