ValueError: Grouper for not 1-dimensional

Question

I\'m have the following code which creates a table and a barplot via seaborn.

#Building a dataframe grouped by the # of Engagement Types
sales_type = sales.g         


        

Answer 1

Happened to me when I accidentally created MultiIndex columns:

>>> values = np.asarray([[1, 1], [2, 2], [3, 3]])

# notice accidental double brackets around column list
>>> df = pd.DataFrame(values, columns=[["foo", "bar"]])

# prints very innocently
>>> df
  foo bar
0   1   1
1   2   2
2   3   3

# but throws this error
>>> df.groupby("foo")
ValueError: Grouper for 'foo' not 1-dimensional

# cause:
>>> df.columns
MultiIndex(levels=[['bar', 'foo']],
           labels=[[1, 0]])

# fix by using correct columns list
>>> df = pd.DataFrame(values, columns=["foo", "bar"])
>>> df.groupby("foo")