CODEWITHSUNDEEP
python
HPJM
HPJM

Reputation: 537

Nested list comprehension to flatten nested list

I'm quite new to Python, and was wondering how I flatten the following nested list using list comprehension, and also use conditional logic.

nested_list = [[1,2,3], [4,5,6], [7,8,9]]

The following returns a nested list, but when I try to flatten the list by removing the inner square brackets I get errors.

odds_evens = [['odd' if n % 2 != 0 else 'even' for n in l] for l in nested_list]

Upvotes: 3

Views: 1009

Answers (4)

Suneel Kushwaha
Suneel Kushwaha

Reputation: 1

What is wrong here ?

>>> nested_list = [[1,2,3], [4,5,6], [7,8,9]]
>>> odds_evens = ['odd' if n % 2 != 0 else 'even' for 1 in nested_list for n in 1]
  File "<stdin>", line 1
SyntaxError: can't assign to literal

Upvotes: 0

MuhammadOsta
MuhammadOsta

Reputation: 88

Read data from Nested list and output to a Flat list based on condition

nested_list = [[1,2,3], [4,5,6], [7,8,9]]

flat_list = [item for sublist in nested_list for item in sublist]
# >>> [1, 2, 3, 4, 5, 6, 7, 8, 9]

flat_list_even = [item for sublist in nested_list for item in sublist if item % 2 == 0]
# >>> [2, 4, 6, 8]


flat_list_odd = [item for sublist in nested_list for item in sublist if item % 2 != 0]
# >>> [1, 3, 5, 7, 9]

flat_list_literal = ["even" if item % 2 == 0 else "odd" for sublist in nested_list for item in sublist]
# >>> ['odd', 'even', 'odd', 'even', 'odd', 'even', 'odd', 'even', 'odd']

Upvotes: 0

amulya349
amulya349

Reputation: 1238

To create a flat list, you need to have one set of brackets in comprehension code. Try the below code:

odds_evens = ['odd' if n%2!=0 else 'even' for n in l for l in nested_list]

Output:

['odd', 'odd', 'odd', 'even', 'even', 'even', 'odd', 'odd', 'odd']

Upvotes: -1

Rakesh
Rakesh

Reputation: 82765

Your syntax was a little wrong. Try below snippet.

nested_list = [[1,2,3], [4,5,6], [7,8,9]]
odds_evens = ['odd' if n % 2 != 0 else 'even' for l in nested_list for n in l]
print(odds_evens)

Output:

['odd', 'even', 'odd', 'even', 'odd', 'even', 'odd', 'even', 'odd']

Nested List Comprehension

Upvotes: 6

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