Quick Answer

Convert multi-dimensional lists to flat lists.

Understanding the Issue

Flattening transforms nested lists into single dimension lists. Methods vary for regular vs. irregular nesting patterns.

The Problem

This code demonstrates the issue:

Python Error 
nested = [[1, 2], [3, [4, 5]], 6]
# Need [1, 2, 3, 4, 5, 6]

The Solution

Here's the corrected code:

Python Fixed 
# Solution 1: List comprehension (1-level)
flat = [item for sublist in nested for item in sublist]

# Solution 2: itertools.chain
from itertools import chain
flat = list(chain.from_iterable(nested))

# Solution 3: Recursive flattening
def flatten(xs):
    for x in xs:
        if isinstance(x, list):
            yield from flatten(x)
        else:
            yield x
flat = list(flatten(nested))

# Solution 4: pandas (for complex data)
import pandas as pd
flat = pd.json_normalize(nested).to_numpy().ravel()

Key Takeaways

Choose flattening method based on nesting depth and structure.