python - 使用 pandas series.sample() 返回索引？

Question

我有一个 pandas 系列，其中一些不同用户的值各不相同。我想做的是从每个用户那里获取一个随机样本，并返回随机样本的索引值。

该系列看起来像这样(每个用户出现在多行中):

index    
row1    user1
row2    user2
row3    user2
row4    user1
row5    user2
row6    user1
row7    user3
...

我写的函数是这样的:

def get_random_sample(series, sample_size, users):
""" Grab a random sample of size sample_size of the tickets resolved by each user in the list users.
    Series has the ticket number as index, and the username as the series values.
    Returns a dict {user:[sample_tickets]}
"""
    sample_dict = {}
    for user in users: 
        sample_dict[user] = series[series==user].sample(n=sample_size, replace=False) 

    return sample_dict

返回的内容如下:

# assuming sample_size is 4
{user1: [user1, user1, user1, user1],
 user2: [user2, user2, user2, user2],
...}

但是我想得到的输出是:

{user1: [row1, row6, row32, row40],
 user2: [row3, row5, row17, row39],
...}
# where row# is the index label for the corresponding row.

基本上我想让 pandas series.sample() 返回随机样本项目的索引而不是项目值。不确定这是否可行，或者我是否最好先重组我的数据(也许将用户作为数据框中的系列名称，而索引成为该系列下的值？但不确定如何执行此操作)。感谢任何见解。

Answer 1

作为@user48956 commented在接受的答案上，使用 numpy.random.choice 对索引进行采样要快得多

np.random.seed(42)
df = pd.DataFrame(np.random.randint(0,100,size=(10000000, 4)), columns=list('ABCD'))
%time df.sample(100000).index
print(_)
%time pd.Index(np.random.choice(df.index, 100000))

Wall time: 710 ms
Int64Index([7141956, 9256789, 1919656, 2407372, 9181191, 2474961, 2345700,
            4394530, 8864037, 6096638,
            ...
             471501, 3616956, 9397742, 6896140,  670892, 9546169, 4146996,
            3465455, 7748682, 5271367],
           dtype='int64', length=100000)
Wall time: 6.05 ms

Int64Index([7141956, 9256789, 1919656, 2407372, 9181191, 2474961, 2345700,
            4394530, 8864037, 6096638,
            ...
             471501, 3616956, 9397742, 6896140,  670892, 9546169, 4146996,
            3465455, 7748682, 5271367],
           dtype='int64', length=100000)