python - 将字符串附加到具有公共(public)列值的数据框中的列表时重复

Question

这里是初学者，我试图根据我分配给他们的聚类值将街区名称与多伦多的数据框隔离开来。我最终得到了一个 2363 项长的列表，而不是包含 3 个唯一项的列表。

Neigh_List = []
for n in toronto_merged['Cluster Labels']:

        if n == 7 :
        x = toronto_merged['Neighborhood']
        Neigh_List.append(x) if x not in Neigh_List else None      


        
               
Neigh_List

[0                                                                                                Parkwoods
 1                                                                                                Parkwoods
 2                                                                                         Victoria Village
 3                                                                                         Victoria Village
 4                                                                                         Victoria Village
                                                        ...                                                
 2359    Mimico NW , The Queensway West , South of Bloor , Kingsway Park South West , Royal York South West
 2360    Mimico NW , The Queensway West , South of Bloor , Kingsway Park South West , Royal York South West
 2361    Mimico NW , The Queensway West , South of Bloor , Kingsway Park South West , Royal York South West
 2362    Mimico NW , The Queensway West , South of Bloor , Kingsway Park South West , Royal York South West
 2363    Mimico NW , The Queensway West , South of Bloor , Kingsway Park South West , Royal York South West
 Name: Neighborhood, Length: 2364, dtype: object]

Answer 1

一般来说，对于较大的数据集(~1000+)，应避免在 Pandas 数据帧上循环，因为 Pandas 内置矢量化函数通常更快(See this other stackoverflow post)。

你可以尝试这样的事情:

neigh_list = list(toronto_merged.loc[toronto_merged['Neighborhood'] == 7]]['Neighborhood'].unique())

另外，如果你想避免列表中的重复项，你可以使用 python sets (see 5.4 at the time of writing) .

unique_elements = set()
for x in some_iterable:
    unique_elements.add(x)

或者，使用集合理解:

unique_elements = {unique_item for unique_item in some_iterable}