How can I use itertools to flatten a nested list in Python?

How can I use itertools to flatten a nested list in Python?

You can use itertools.chain.from_iterable() to flatten a nested list. Here's an example:

import itertools
nested_list = [[1, 2, 3], [4, 5], [6]]
flattened = list(itertools.chain.from_iterable(nested_list))
print(flattened)  # Output: [1, 2, 3, 4, 5, 6]

What if I have a more complex nested structure?

For more complex structures, you might need a recursive approach. Here's a function that handles deeper nesting:

def flatten(nested):
    for item in nested:
        if isinstance(item, list):
            yield from flatten(item)
        else:
            yield item

nested_list = [1, [2, [3, 4], 5], 6]
flattened = list(flatten(nested_list))
print(flattened)  # Output: [1, 2, 3, 4, 5, 6]

Can I use list comprehensions instead?

Yes, you can use list comprehensions to flatten a list, but it works best for one level of nesting. For example:

nested_list = [[1, 2, 3], [4, 5], [6]]
flattened = [item for sublist in nested_list for item in sublist]
print(flattened)  # Output: [1, 2, 3, 4, 5, 6]

Are there any performance differences between these methods?

Yes, performance can vary. itertools.chain is generally faster for large lists, while list comprehensions are more readable for simpler cases. Recursive functions can be slower due to function call overhead.