熊猫-将多个数据框写入单个Excel工作表

Question

I have a dataframe with 45 columns and 1000 rows. My requirement is to create a single excel sheet with the top 2 values of each column and their percentages (suppose col 1 has the value 'python' present 500 times in it, the percentage should be 50)

I used:

    writer = pd.ExcelWriter('abc.xlsx')
    df = pd.read_sql('select * from table limit 1000', <db connection sring>)
    column_list = df.columns.tolist()
    df.fillna("NULL", inplace = True)
    for obj in column_list:
        df1 = pd.DataFrame(df[obj].value_counts().nlargest(2)).to_excel(writer,sheet_name=obj
writer.save()

This writes the output in separate excel tabs of the same document. I need them in a single sheet in the below format:

Column Name          Value         Percentage
col1                 abc           50
col1                 def           30
col2                 123           40
col2                 456           30

....

Let me know any other functions as well to get to this output.

Answer 1

The first thing that jumps out to me is that you are changing the sheet name each time, by saying sheet_name=obj If you get rid of that, that alone might fix your problem.

If not, I would suggest concatenating the results into one large DataFrame and then writing that DataFrame to Excel.

for obj in column_list:
    df = pd.DataFrame(df[obj].value_counts().nlargest(2))
    if df_master is None:
        df_master = df
    else:
        df_master = pd.concat([df_master,df])
df_master.to_excel("abc.xlsx")

Here's more information on stacking/concatenating dataframes in Pandas https://pandas.pydata.org/pandas-docs/stable/user_guide/merging.html