def function 中的 KeyError

Question

I am transforming some data and I found myself in the situation where I needed to repeat the same process across different dataframes so I thought that building a function would be great.

I started doing this:

count_words = lambda x: len(x)
index = 'word_count'
values= ['Search term', 'Clicks', 'Impr.']

def table_transformation(dataframe, index, values):
    dataframe_to_pivot = pd.pivot_table(data= dataframe,
                                        index= index,
                                        values= values,
                                        aggfunc= {values[0]: count_words,
                                                  values[1]: np.sum,
                                                  values[2]: np.sum}
                                       )
    
    dataframe_to_pivot.sort_values(by=[index], ascending= True)
    sum_counts = dataframe_to_pivot.iloc[9:].sum()
    dataframe_to_pivot.drop(dataframe_to_pivot.index[9:].tolist())
    dataframe_to_pivot.loc['+10'] = sum_counts
    return dataframe_to_pivot

fy21_word_counts = fy21.apply(table_transformation, args=(index, values))
fy21_word_counts

I got a KeyError: 'Search term' error .

What I tried:

• I tried inserting the actual names of the columns inside the function but got the same error
• the logic inside the function works outside the function's def() structure

What is it that I overlooked/ misunderstood?

Thank you for your time.

Answer 1

Use DataFrame.pipe , because need pass DataFrame instead apply function for each column by .apply :

fy21_word_counts = fy21.pipe(table_transformation, index, values)