Python remove nested list from list

Example 1: Using List Comprehension

my_list = [[1], [2, 3], [4, 5, 6, 7]] flat_list = [num for sublist in my_list for num in sublist] print[flat_list]

Output

[1, 2, 3, 4, 5, 6, 7]

This is one of the simplest pythonic ways of flattening a list.

• Using list comprehension access the sublist from my_list, then access each element of the sublist.
• Each element num is stored in flat_list.

Learn more about list comprehension at Python List Comprehension.

Example 2: Using Nested for Loops [non pythonic way]

my_list = [[1], [2, 3], [4, 5, 6, 7]] flat_list = [] for sublist in my_list: for num in sublist: flat_list.append[num] print[flat_list]

Output

[1, 2, 3, 4, 5, 6, 7]

• Create an empty list flat_list.
• Access each element of the sublist using a nested loop and append that element to flat_list.

Example 3: Using itertools package

import itertools my_list = [[1], [2, 3], [4, 5, 6, 7]] flat_list = list[itertools.chain[*my_list]] print[flat_list]

Output

[1, 2, 3, 4, 5, 6, 7]

Using itertools module, we can create a flattened list.

• chain[] method from itertools module returns each element of each iterable [i.e. sub lists ].
• list[] converts those returned values into a list.

Example 4: Using sum[]

my_list = [[1], [2, 3], [4, 5, 6, 7]] flat_list = sum[my_list, []] print[flat_list]

Output

[1, 2, 3, 4, 5, 6, 7]

• Provide two arguments to the sum[] method: my_list and an empty list [i.e. [ ]].
• sum[] combines my_list and [ ] to produce a flattened list.

Example 5: Using lambda and reduce[]

from functools import reduce my_list = [[1], [2, 3], [4, 5, 6, 7]] print[reduce[lambda x, y: x+y, my_list]]

Output

[1, 2, 3, 4, 5, 6, 7]

In the above example, reduce[] applies the lambda function to all the elements of my_list.

Learn more about lambda expressions at Python Anonymous/Lambda Function.