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I have a Pandas dataframe which I am grouping by one of the columns in the dataframe. Then I have a function which needs to be applied once to each group. The function modifies the group. So what I want to do is something like this:

df = pd.DataFrame([[1, 'coupe', 2004], [2, 'sedan', 2004], [1, 'sedan', 2015], [3, 'coupe', 2010]], columns=['group_id', 'model', 'year_manufactured'])
group_id model year_manufactured
0 1 coupe 2004
1 2 sedan 2004
2 1 sedan 2015
3 3 coupe 2010 
def my_function(group):
    if 'coupe' in group['model']:
        group['model'].replace('coupe', 'hatchback', inplace=True)
        group['year_manufactured'].replace(2004, 2005, inplace=True)
    else:
        newest_car = group['year_manufactured'].idxmax()
        newest_car_type = group.loc[newest_car, 'model']
        group['model'] = group['model'].map(lambda x : x + newest_car_type)

df.groupby('group_id').map(my_function)

However, map can't be applied to a groupby. Is there any way I can work around this while not compromising speed. Also the function I have can't just be mapped to each row of the database since the way it acts on one row is dependent on previous rows.

Panda
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    [How to make good reproducible pandas examples](https://stackoverflow.com/questions/20109391/how-to-make-good-reproducible-pandas-examples) – It_is_Chris Jun 24 '21 at 19:28
  • If you don't want to compromise speed, don't use `apply` or map with a function. – ifly6 Jun 24 '21 at 19:29
  • what does `my_function` do, there's probably an alternative – ALollz Jun 24 '21 at 19:43
  • @It_is_Chris I added some more clarification and an example of what this would look like. Are you able to answer my question now? – Panda Jun 24 '21 at 21:43
  • @ALollz the function edits the group based on the characteristics of a group. I wrote in an example of what the function would look like. – Panda Jun 24 '21 at 21:46
  • Could you please add what would be the output of applying `my_function` to your question? – Chicodelarose Jun 27 '21 at 00:05
  • @Chicodelarose my_function is not supposed to return anything. It is merely supposed to modify the groups – Panda Jun 28 '21 at 22:26

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