I have following dataframe in pandas
code tank nozzle_1 nozzle_2 nozzle_var nozzle_sale
123 1 1 1 10 10
123 1 2 2 12 10
123 2 1 1 10 10
123 2 2 2 12 10
123 1 1 1 10 10
123 2 2 2 12 10
Now, I want to generate cumulative sum of all the columns grouping over tank and take out the last observation. nozzle_1 and nozzle_2 columns are dynamic, it could be nozzle_3, nozzle_4....nozzle_n etc. I am doing following in pandas to get the cumsum
## Below code for calculating cumsum of dynamic columns nozzle_1 and nozzle_2
cols= df.columns[df.columns.str.contains(pat='nozzle_\d+$', regex=True)]
df.assign(**df.groupby('tank')[cols].agg(['cumsum'])\
.pipe(lambda x: x.set_axis(x.columns.map('_'.join), axis=1, inplace=False)))
## nozzle_sale_cumsum is static column
df[nozzle_sale_cumsum] = df.groupby('tank')['nozzle_sale'].cumsum()
From above code I will get cumsum of following columns
tank nozzle_1 nozzle_2 nozzle_var nozzle_1_cumsum nozzle_2_cumsum nozzle_sale_cumsum
1 1 1 10 1 1 10
1 2 2 12 3 3 20
2 1 1 10 1 1 10
2 2 2 12 3 3 20
1 1 1 10 4 4 30
2 2 2 12 5 5 30
Now, I want to get last values of all 3 cumsum columns grouping over tank. I can do it with following code in pandas, but it is hard coded with column names.
final_df= df.groupby('tank').agg({'nozzle_1_cumsum':'last',
'nozzle_2_cumsum':'last',
'nozzle_sale_cumsum':'last',
}).reset_index()
Problem with above code is nozzle_1_cumsum and nozzle_2_cumsum is hard coded which is not the case. How can I do this in pandas with dynamic columns.
How about:
df.filter(regex='_cumsum').groupby(df['tank']).last()
Output:
nozzle_1_cumsum nozzle_2_cumsum nozzle_sale_cumsum
tank
1 4 4 30
2 5 5 30
You can also replace df.filter(...)
by, eg, df.iloc[:,-3:]
or df[col_names]
.
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