1

我正在尝试从列表和元组的元组创建字典，如下图所示。我必须将元组反向映射到列表并创建一组非无列名。

非常感谢有关实现解决方案（所需字典）的 pythonic 方式的任何建议。

MySQL 表“状态日志”：

Name NY   TX   NJ
Amy  1    None 1
Kat  None 1    1
Leo  None None 1

蟒蛇代码：

## Fetching data from MySQL table
#cursor.execute("select * from statelog")
#mydataset = cursor.fetchall()
## Fetching column names for mapping
#state_cols = [fieldname[0] for fieldname in cursor.description]

state_cols = ['Name', 'NY', 'TX', 'NJ']
mydataset = (('Amy', '1', None, '1'), ('Kat', None, '1', '1'), ('Leo', None, None, '1'))

temp = [zip(state_cols, each) for each in mydataset]

# Looks like I can't do a tuple comprehension for the following snippet : finallist = ((eachone[1], eachone[0]) for each in temp for eachone in each if eachone[1] if eachone[0] == 'Name')
for each in temp:
    for eachone in each:
        if eachone[1]:
            if eachone[0] == 'Name':
                k = eachone[1]
            print k, eachone[0]

print '''How do I get a dictionary in this format'''            
print '''name_state = {"Amy": set(["NY", "NJ"]),
                "Kat": set(["TX", "NJ"]),
                "Leo": set(["NJ"])}'''

到目前为止的输出：

Amy Name
Amy NY
Amy NJ
Kat Name
Kat TX
Kat NJ
Leo Name
Leo NJ

所需的字典：

name_state = {"Amy": set(["NY", "NJ"]),
              "Kat": set(["TX", "NJ"]),
              "Leo": set(["NJ"])}
4

3 回答 3

1

看起来像defaultdict的另一份工作！

所以让我们创建我们的默认字典

name_state = collections.defaultdict(set)

我们现在有一个字典，其中包含所有默认值，我们现在可以做这样的事情

name_state['Amy'].add('NY')

继续前进，您只需要遍历您的对象并为每个名称添加正确的状态。享受

于 2012-06-01T15:50:08.653 回答
1

您可以将其作为字典理解（Python 2.7+）：

from itertools import compress
name_state = {data[0]: set(compress(state_cols[1:], data[1:])) for data in mydataset}

或作为生成器表达式：

name_state = dict((data[0], set(compress(state_cols[1:], data[1:]))) for data in mydataset)
于 2012-06-01T15:50:41.377 回答
1

老实说，我想说你的问题是你的代码变得太麻烦了。抵制“单衬”它的诱惑，创造一个功能。一切都会变得更容易！

mydataset = (
        ('Amy', '1', None, '1'),
        ('Kat', None, '1', '1'),
        ('Leo', None, None, '1')
)

def states(cols, data):
    """
    This function receives one of the tuples with data and returns a pair
    where the first element is the name from the tuple, and the second
    element is a set with all matched states. Well, at least *I* think
    it is more readable :)
    """
    name = data[0]
    states = set(state for state, value in zip(cols, data) if value == '1')
    return name, states

pairs = (states(state_cols, data) for data in mydataset)
# Since dicts can receive an iterator which yields pairs where the first one
# will become a key and the second one will become the value, I just pass
# a list with all pairs to the dict constructor.
print dict(pairs)

结果是：

{'Amy': set(['NY', 'NJ']), 'Leo': set(['NJ']), 'Kat': set(['NJ', 'TX'])}
于 2012-06-01T15:51:02.007 回答