如何在Python3中计算排行榜排名？实现指定分数排名转换

Great question! Let's walk through a few practical, efficient ways to convert your score list into the desired ranking list—where tied scores get the same rank, and subsequent ranks skip the number of tied entries.

Method 1: Using a Dictionary (No External Libraries, Efficient) #

This approach is straightforward and works well for most cases, especially if you want to avoid dependencies. Here's how it works:

1. Extract unique scores and sort them in descending order.
2. Create a mapping from each score to its corresponding rank (starting at 1).
3. Iterate over your original score list and replace each score with its rank from the mapping.

scores = [100, 100, 50, 40, 40, 20, 10]

# Get unique scores sorted from highest to lowest
unique_sorted_scores = sorted(set(scores), reverse=True)

# Create a dictionary to map each score to its rank
rank_mapping = {score: idx + 1 for idx, score in enumerate(unique_sorted_scores)}

# Generate the ranking list
rankings = [rank_mapping[score] for score in scores]

print(rankings)  # Output: [1, 1, 2, 3, 3, 4, 5]

Method 2: Using Pandas (Perfect for Data Workflows) #

If you're already working with pandas (common in data analysis), the rank() method makes this trivial. We'll use method='min' to ensure tied scores get the same rank, and ascending=False to rank highest scores first.

import pandas as pd

scores = [100, 100, 50, 40, 40, 20, 10]
score_series = pd.Series(scores)

# Calculate ranks, convert to integers, then to a list
rankings = score_series.rank(method='min', ascending=False).astype(int).tolist()

print(rankings)  # Output: [1, 1, 2, 3, 3, 4, 5]

Method 3: Manual Index Lookup (Simple, but Less Efficient for Large Data) #

For small datasets, you can directly use the index() method on a sorted list to find the first occurrence of each score, then add 1 to get the rank. Note that this has a time complexity of O(n²) since index() scans the list each time, so it's not ideal for very large lists.

scores = [100, 100, 50, 40, 40, 20, 10]

# Sort the scores in descending order
sorted_scores = sorted(scores, reverse=True)

# For each score, find its first position in the sorted list and add 1 for rank
rankings = [sorted_scores.index(score) + 1 for score in scores]

print(rankings)  # Output: [1, 1, 2, 3, 3, 4, 5]

All three methods will give you the exact ranking list you're looking for. Pick the one that best fits your project's context!

内容的提问来源于stack exchange，提问作者user9342203