flat 2d to 1d array-CodePudding

I have a list with a list inside.

Can you please help me - how to change the list of lists to list?

I tried with nd.array reshape(), flatten(), and ravel(), but no luck

Input:

['Test', [1, 2]]

Expected result:

['Test', 1, 2]

CodePudding user response：

This problem is known as flattening an irregular list. There are a few ways you can do this -

Using list comprehension

l = ['Test', [1, 2]]

regular_list = [i if type(i)==list else [i] for i in l]
flatten_list = [i for sublist in regular_list for i in sublist]
flatten_list

['Test', 1, 2]

Using nested for loops

out = []
for i in l:
    if type(i)==list:
        for j in i:
            out.append(j)
    else:
        out.append(i)
print(out)

['Test', 1, 2]

CodePudding user response：

There are multiple answers, depending on context and preference:

For python lists:

flattened_list = [element for sublist in input_list for element in sublist]

# or:

import itertools

flattened_list = itertools.chain(*input_list)

Or, if you are using numpy.

flattened_list = list(original_array.flat)

# or, if you need it as a numpy array:

flattened_array = original_array.flatten()

CodePudding user response：

You can try this:

li = ['Test', [1, 2]]

merged = []
for x in li:
  if not isinstance(x, list):
    merged.append(x)
  else:
    merged.extend(x)

print(merged)

Output: ['Test', 1, 2]