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I have a big pandas dataframe from which I'm trying to select some rows with the .loc tool. The problem is that the condition I want to use in it needs an index which is given in one of the columns of the dataframe (the 'index' one). I try to select the row if the value is below a value that I need to found with the index in a simple list.

>>> df
r   v   index
1   2   2
2   4   3
3   20  1

>>> list
[3,6,32]

I want something like:

df.loc[ df['v'] < list[ df['index'] ] ]

So something which refers to the index in the studied row of the dataframe.

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1 Answer 1

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IIUC, convert the list to an array, and use "index" as the indexer:

v = np.array([3,6,32])
df[df['v'] < v[df['index'] - 1]]

   r  v  index
0  1  2      2
1  2  4      3

Where,

v[df['index'] - 1]
# array([ 6, 32,  3])

r = df.loc[df['v'] < v[df['index'] - 1]].copy()
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