将具有相同键的dict组合成一个具有lis的dict

Question

我有一个dicts元组，作为mysql服务器的答案。你知道吗

({
    'firstname': 'Alexandro',
    'Title': 'My life',
    'lastname': 'Riviera',
    'articles.id': 6L,
    'authorId': 1L,
    'id': 1L
}, {
    'firstname': 'Alexandro',
    'Title': 'My life 2',
    'lastname': 'Riviera',
    'articles.id': 7L,
    'authorId': 1L,
    'id': 1L
}, {
    'firstname': 'Helen',
    'Title': 'Learn SQL',
    'lastname': 'Oldgarno',
    'articles.id': 8L,
    'authorId': 2L,
    'id': 2L
}, {
    'firstname': 'Helen',
    'Title': 'SQL for you',
    'lastname': 'Oldgarno',
    'articles.id': 9L,
    'authorId': 2L,
    'id': 2L
})

我想通过相同的键“authord”转换成：

({
    'firstname': 'Alexandro',
    'lastname': 'Riviera',
    'id': 1L,
    'articles': [{
        'articles.id': 6L,
        'authorId': 1L,
        'Title': 'My life'
    }, {
        'articles.id': 7L,
        'authorId': 1L,
        'Title': 'My life 2'
    }]
}, {
    'firstname': 'Helen',
    'lastname': 'Oldgarno',
    'id': 2L,
    'articles': [{
        'articles.id': 8L,
        'authorId': 2L,
        'Title': 'Learn SQL'
    }, {
        'articles.id': 9L,
        'authorId': 2L,
        'Title': 'SQL for you'
    }]
})

我不知道如何以一种不太难看的方式完成这项任务。任何建议都会有帮助！你知道吗

Answer 1

您可以将其转换为列表并按authord排序。一旦您能够基于authord将它们分开，您就可以完全折叠author信息字段并将文章信息放入列表中。你知道吗

Answer 2

可以编写这样的合并函数，但确实应该考虑重写SQL查询。下面是一个简单的解决方案：

def merge_books(books):
    merged = {}

    for book in books:
        authorId = book['authorId']

        # Create article attribute
        book['articles'] = [{
            'articles.id': book['articles.id'],
            'authorId':    book['authorId'],
            'Title':       book['Title'],
        }]

        # Remove redundant information
        del book['articles.id']
        del book['authorId']
        del book['Title']

        if authorId in merged:
            merged[authorId]['articles'].append(book['articles'][0])
        else:
            merged[authorId] = book

    # Convert dict into a tuple, but why not a list?
    return tuple(merged.values())

更好的方法是使用两个select语句并将其结果合并在一起：

import MySQLdb

def get_authors_with_articles(connection):
    cursor = connection.cursor()

    authors = {}
    for author in cursor.execute('SELECT * FROM Authors'):
        # Initialize empty article list that will be popluated with the next select
        author['articles'] = []
        authors[author['id']] = author

    for article in cursor.execute('SELECT * FROM Articles').fetchall():
        # Fetch and delete redundant information
        author_id = article['authorId']
        del article['authorId']

        authors[author_id]['articles'].append(article)

    return list(authors.values())


if __name__ == '__main__':
    connection = MySQLdb.connect(
        mysql_host,
        mysql_user,
        mysql_pass,
        mysql_base,
        cursorclass=MySQLdb.cursors.DictCursor
    )
    print(get_authors_with_articles(connection))