Python：将元组列表按指定条件转换为字典

Here's a straightforward, readable solution to transform your list of tuples into the desired dictionary, including logic to retain only the latest 'End' entry for each book:

# Sample input list
Book = [
    (24, '2008-10-30', 'Start'),
    (24, '2008-12-20', 'End', 'sold'),
    (24, '2009-02-04', 'End', 'sold'),
    (24, '2009-11-25', 'End', 'sold'),
    (25, '2009-01-01', 'Start'),
    (25, '2009-11-14', 'End', 'returned'),
    (26, '2010-04-03', 'Start'),
    (26, '2010-10-11', 'End', 'sold')
]

# Initialize empty result dictionary
bookDict = {}

for item in Book:
    book_id = item[0]
    date = item[1]
    status = item[2]
    
    # Create a blank entry for the book if it doesn't exist yet
    if book_id not in bookDict:
        bookDict[book_id] = {}
    
    if status == 'Start':
        # Assign the start date (assumes one Start entry per book; overwrites if multiple exist)
        bookDict[book_id]['Start'] = date
    elif status == 'End':
        reason = item[3]
        # Only update if no End exists yet, or current date is later than stored date
        # (YYYY-MM-DD strings can be compared directly for chronological order)
        if 'End' not in bookDict[book_id] or date > bookDict[book_id]['End']:
            bookDict[book_id]['End'] = date
            bookDict[book_id]['reason'] = reason

# Print the final result
print(bookDict)

Key Logic Explanations: #

• Initialization: We start with an empty dictionary to build our result.
• Book Entry Setup: For each tuple, we first ensure the book ID has an entry in the dictionary to avoid KeyError.
• Start Record Handling: Directly assign the start date to the book's entry (works even if multiple Start entries exist, though it will use the last one encountered).
• End Record Handling: We check if there's no existing End date, or if the current End date is later than the stored one. Since dates are in YYYY-MM-DD format, string comparison works perfectly for chronological ordering. We update both the End date and reason whenever we find a newer End record.

Output Result: #

When you run the code, you'll get exactly the structure you need:

{
 24: {'Start': '2008-10-30', 'End': '2009-11-25', 'reason': 'sold'},
 25: {'Start': '2009-01-01', 'End': '2009-11-14', 'reason': 'returned'},
 26: {'Start': '2010-04-03', 'End': '2010-10-11', 'reason': 'sold'}
}

内容的提问来源于stack exchange，提问作者MahsaAzizi