蟒蛇如何根据属性的对象使用计数器 [英] Python how to use Counter on objects according to attributes

问题描述

我有一个名为记录类，其中存储日志记录的信息;

I have a class named record, which stores information of log record;

class Record():
    def __init__(self, **kwargs):
        for key, value in kwargs.items():
             setattr(self, key, value)

和该记录的例子可以是：

And examples of this record can be:

r1 = Record(uid='001',url='www.google.com',status=200)
r2 = Record(uid='002',url='www.google.com',status=404)
r3 = Record(uid='339',url='www.ciq.com', status=200)
...

我要的是计算每个URL有多少用户了。因此，对谷歌，也有'001'和'002'。我通常使用一个计数器来记录列表，其外观中的元素。但在这里，似乎柜台干脆把元素，而不是指望他们。是否有一个lambda我可以把或尝试？

What I want is to count how many users each url has. So for "google", there are '001' and '002'. I usually use a Counter to record elements within a list and their appearances. But here, Counter seems just put the elements instead of counting them. Is there a lambda I can put or try?

我可以去通过全体员工虽然...

I can go through all the staff though...

我想我可能会在这里引起混乱。

I think i may cause confusion here.

我的重点是通过组其属性的对象。所以，不仅网址计数，而且，

My key point is to group the objects by its attributes...So not only the url counting but also,

res = Counter(r)

（不知道如何把里面的λ，甚至可能的话）我可以得到也许

(don't know how to put lambda inside or even that's possible) I can get maybe

res[0].url = 'www.google.com'

和计数为2 ..？

和建议？

谢谢！

推荐答案

有在我的previous回答一个微妙的bug，虽然修复它，我想出了一个更简单，更快捷的方式做事情不再使用 itertools.groupby（）。

There was a subtle bug in my previous answer, and while fixing it I came up with a much simpler and faster way to do things which no longer uses itertools.groupby().

下面现在的更新code特点设计做的正是你想要的功能。

The updated code below now features a function designed to do exactly what you want.

from collections import Counter
from operator import attrgetter

class Record(object):
    def __init__(self, **kwargs):
        for key, value in kwargs.iteritems():
             setattr(self, key, value)

records = [Record(uid='001', url='www.google.com', status=200),
           Record(uid='002', url='www.google.com', status=404),
           Record(uid='339', url='www.ciq.com',    status=200)]

def count_attr(attr, records):
    """ Returns Counter keyed by unique values of attr in records sequence. """
    get_attr_from = attrgetter(attr)
    return Counter(get_attr_from(r) for r in records)

for attr in ('status', 'url'):
    print('{!r:>8}: {}'.format(attr, count_attr(attr, records)))

输出：

'status': Counter({200: 2, 404: 1})
   'url': Counter({'www.google.com': 2, 'www.ciq.com': 1})

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