Pandas groupby to to_csv

Question

Want to output a Pandas groupby dataframe to CSV. Tried various StackOverflow solutions but they have not worked.

Python 3.6.1, Pandas 0.20.1

groupby result

Answer 1

Try changing your second line to week_grouped = week_grouped.sum() and re-running all three lines.

If you run week_grouped.sum() in its own Jupyter notebook cell, you'll see how the statement returns the output to the cell's output, instead of assigning the result back to week_grouped. Some pandas methods have an inplace=True argument (e.g., df.sort_values(by=col_name, inplace=True)), but sum does not.

EDIT: does each week number only appear once in your CSV? If so, here's a simpler solution that doesn't use groupby:

df = pd.read_csv('input.csv')
df[['id', 'count']].to_csv('output.csv')