IOB format merge

Question

I have a dataframe in IOB format as below:-

Name	Label
Alan	B-PERSON
Smith	I-PERSON
is	O
Alice's	B-PERSON
uncle	O
from	O
New	B-LOCATION
York	I-LOCATION
city	I-LOCATION

I would like to convert into a new dataframe as below:-

Name	Label
Alan Smith	PERSON
Alice's	PERSON
New York city	LOCATION

Any help is much appreciated!

Answer 1

You can create groups by compare values O, remove IO- values in Label column and with helper groups created by cumulative sum aggregate join:

m = df['Label'].eq('O')

df = (df[~m].assign(Label=lambda x: x['Label'].str.replace('^[IB]-', ''))
            .groupby([m.cumsum(), 'Label'])['Name']
            .agg(' '.join)
            .droplevel(0)
            .reset_index()
            .reindex(df.columns, axis=1))
print (df)
            Name     Label
0     Alan Smith    PERSON
1        Alice's    PERSON
2  New York city  LOCATION