嵌套列表转换问题：合并含空元素列表生成目标输出结构

Let's walk through why your current code isn't producing the desired output, then build a working solution step by step.

Your Problem Recap #

You have this input list:

original_list = [['a','b','c',''],['c','e','f'],['c','g','h']]

And you want to merge it into:

[['a','b','c','e','f'],['a','b','c','g','h']]

The rule: when a sublist ends with an empty string '', use its non-empty prefix as a base, then merge it with all sublists that start with the last element of that base.

What's Wrong With Your Current Code #

Your approach has a few key issues:

• You're modifying the original list's elements directly instead of creating new, clean result lists
• You don't remove the trailing empty string from the "base" sublist
• The combine function's if not m in x check skips elements unnecessarily (we know we only need to avoid the duplicate starting element of the secondary lists)
• There's no logic to collect and return the final merged lists as a proper result

Working Solution #

Here's a function that implements your desired behavior clearly:

def merge_nested_lists(mylist):
    # Step 1: Find the base template (sublist ending with empty string)
    base_template = None
    for sublist in mylist:
        # Check if the sublist isn't empty and ends with ''
        if sublist and sublist[-1] == '':
            # Extract the non-empty part as our base
            base_template = sublist[:-1]
            break
    
    # If no template found, return original list
    if not base_template:
        return mylist.copy()
    
    # Step 2: Merge base with matching sublists
    merged_result = []
    for sublist in mylist:
        # Skip the original template sublist, and check if sublist starts with base's last element
        if sublist != base_template + [''] and sublist[0] == base_template[-1]:
            # Merge base with sublist (skip the duplicate first element of sublist)
            merged = base_template + sublist[1:]
            merged_result.append(merged)
    
    return merged_result

# Test it out
original_list = [['a','b','c',''],['c','e','f'],['c','g','h']]
print(merge_nested_lists(original_list))
# Output: [['a', 'b', 'c', 'e', 'f'], ['a', 'b', 'c', 'g', 'h']]

How This Works #

1. Find the Base Template: We loop through the input list to find the sublist ending with '', then strip that empty string to get our base (['a','b','c']).
2. Merge Matching Sublists: We iterate through the input again, looking for sublists that start with the last element of our base ('c'). For each match, we merge the base with the sublist (skipping the duplicate starting 'c' to avoid redundancy).
3. Return Clean Result: We collect all merged lists and return them as the final output.

Edge Case Handling #

• If no sublist ends with '', the function returns a copy of the original list to avoid modifying the input.
• It skips the original template sublist to prevent including it in the result.

内容的提问来源于stack exchange，提问作者baha joher