# Python | Ways to flatten a 2D list

Given a 2D list, write a Python program to convert the given list into a flattened list.

Method #1: Using` chain.iterable()`

 `# Python code to demonstrate  ` `# converting 2d list into 1d list ` `# using chain.from_iterables ` ` `  `# import chain ` `from` `itertools ``import` `chain ` ` `  `ini_list ``=` `[[``1``, ``2``, ``3``], ` `            ``[``3``, ``6``, ``7``], ` `            ``[``7``, ``5``, ``4``]] ` `             `  `# printing initial list ` `print` `(``"initial list "``, ``str``(ini_list)) ` ` `  `# converting 2d list into 1d ` `# using chain.from_iterables ` `flatten_list ``=` `list``(chain.from_iterable(ini_list)) ` ` `  `# printing flatten_list ` `print` `(``"final_result"``, ``str``(flatten_list)) `

Output:

```initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]
```

Method #2: Using list comprehension

 `# Python code to demonstrate  ` `# converting 2d list into 1d list ` `# using list comprehension ` ` `  `# import chain ` `from` `itertools ``import` `chain ` ` `  `ini_list ``=` `[[``1``, ``2``, ``3``], ` `            ``[``3``, ``6``, ``7``], ` `            ``[``7``, ``5``, ``4``]] ` `             `  `# printing initial list ` `print` `(``"initial list "``, ``str``(ini_list)) ` ` `  `# converting 2d list into 1d ` `# using list comprehension ` `flatten_list ``=` `[j ``for` `sub ``in` `ini_list ``for` `j ``in` `sub] ` ` `  `# printing flatten_list ` `print` `(``"final_result"``, ``str``(flatten_list)) `

Output:

```initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]
```

Method #3: Using `functools.reduce`

 `# Python code to demonstrate  ` `# converting 2d list into 1d list ` `# using functools.reduce ` ` `  `# import functools ` `from` `functools ``import` `reduce` ` `  `ini_list ``=` `[[``1``, ``2``, ``3``], ` `            ``[``3``, ``6``, ``7``], ` `            ``[``7``, ``5``, ``4``]] ` `             `  `# printing initial list ` `print` `(``"initial list "``, ``str``(ini_list)) ` ` `  `# converting 2d list into 1d ` `# using functools.reduce ` `flatten_list ``=` `reduce``(``lambda` `z, y :z ``+` `y, ini_list) ` ` `  `# printing flatten_list ` `print` `(``"final_result"``, ``str``(flatten_list)) `

Output:

```initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]
```

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