在 pandas 中,如何基于多个列的组合创建唯一的ID? [英] In Pandas, how to create a unique ID based on the combination of many columns?
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问题描述
我有一个非常大的数据集,看起来像
I have a very large dataset, that looks like
df = pd.DataFrame({'B': ['john smith', 'john doe', 'adam smith', 'john doe', np.nan], 'C': ['indiana jones', 'duck mc duck', 'batman','duck mc duck',np.nan]})
df
Out[173]:
B C
0 john smith indiana jones
1 john doe duck mc duck
2 adam smith batman
3 john doe duck mc duck
4 NaN NaN
我需要创建一个ID变量,该变量对于每个B-C组合都是唯一的.也就是说,输出应为
I need to create a ID variable, that is unique for every B-C combination. That is, the output should be
B C ID
0 john smith indiana jones 1
1 john doe duck mc duck 2
2 adam smith batman 3
3 john doe duck mc duck 2
4 NaN NaN 0
我实际上并不关心索引是否从零开始,以及缺少的列的值是0还是任何其他数字.我只想要快速的东西,不需要太多的内存并且可以快速排序. 我使用:
I actually dont care about whether the index starts at zero or not, and whether the value for the missing columns is 0 or any other number. I just want something fast, that does not take a lot of memory and can be sorted quickly. I use:
df['combined_id']=(df.B+df.C).rank(method='dense')
,但输出为float64
,并占用大量内存.我们可以做得更好吗?
谢谢!
but the output is float64
and takes a lot of memory. Can we do better?
Thanks!
推荐答案
I think you can use factorize
:
df['combined_id'] = pd.factorize(df.B+df.C)[0]
print df
B C combined_id
0 john smith indiana jones 0
1 john doe duck mc duck 1
2 adam smith batman 2
3 john doe duck mc duck 1
4 NaN NaN -1
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