pandas filter large dataframe and order by a list

Question

I have a large dataframe as follows:

master_df

             result   item
0            5        id13
1            6        id23432
2            3        id2832
3            4        id9823
......
84376253     7        id9632

And another smaller dataframe as follows:

df = pd.DataFrame({'item' : ['id9632', 'id13', 'id2832', 'id2342']})

How can I extract the relevant elements from master_df.result to match with df.item so I can achieve the following:

df = df.assign(result=list_of_results_in_order)

YOLO · Accepted Answer · 2018-04-15 17:44:21Z

1

You can do merge also:

df = df.merge(master_df, on='item', how='left)

answered Apr 15, 2018 at 17:44

YOLO

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jezrael · Accepted Answer · 2018-04-15 17:20:00Z

1

I think need isin with boolean indexing:

#for Series
s = master_df.loc[master_df['item'].isin(df['item']),'result']
print (s)
0           5
2           3
84376253    7
Name: result, dtype: int64

#for list
L = master_df.loc[master_df['item'].isin(df['item']),'result'].tolist()
print (L)
[5, 3, 7]

#for DataFrame
df1 = master_df[master_df['item'].isin(df['item'])]
print (df1)
          result    item
0              5    id13
2              3  id2832
84376253       7  id9632

edited Apr 15, 2018 at 17:20

answered Apr 15, 2018 at 17:13

jezrael

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