[Python] Get most recent value based on date column, grouped by id column

I want to get a subset of this data so that I only have the most recent value for each obj_id, with "most recent" meaning largest data_date.

obj_id data_date value
0 4 2011-11-01 59500
1 2 2011-10-01 35200
2 4 2010-07-31 24860
3 1 2009-07-28 15860
4 2 2008-10-15 200200


I've hacked together a solution, but it feels dirty. I was wondering if anyone has a better way. I'm sure I must be missing some easy way to do it through pandas.

My method is essentially to group, sort, retrieve, and recombine as follows:

row_arr = []
for grp, grp_df in df.groupby('obj_id'):
row_arr.append(dfg.sort('data_date', ascending=False)[:1].values[0])

df_new = DataFrame(row_arr, columns=('obj_id', 'data_date', 'value'))

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