Unhelpful error message when groupby() called with a column that is duplicated

[cpbl]

The following code:

import pandas as pd
p1 = {'name': 'willy', 'age': 10}
p2 = {'name': 'willy', 'age': 11}
p3 = {'name': 'zoe', 'age': 10}
df = pd.DataFrame([p1, p2, p3])
df = df[['name','name','age']]
df.groupby('name')

gives the following error:

TypeError: 'DataFrame' object is not callable

Instead, it should say "Cannot groupby a column which exists more than once"

[jreback]

that does seem unhelpful!

care to do a pull-request to fix (prob just catch the TypeError in core/groupby.pythen if its a duplicate raise maybe a ValueError) ?

[hayd]

came up on SO (a couple of times) http://stackoverflow.com/q/25624022/1240268 http://stackoverflow.com/q/21172271/1240268

[jreback]

closed by #8210