Getting AttributeError 'Workbook' object has no attribute 'add_worksheet' - while writing data frame to excel sheet

Question

I have the following code, and I am trying to write a data frame into an "existing" worksheet of an Excel file (referred here as test.xlsx). Sheet3 is the targeted

Answer 1

You can use openpyxl as the engine when you are creating an instance of pd.ExcelWriter.

import pandas as pd
import openpyxl

df1 = pd.DataFrame({'A':[1, 2, -3],'B':[1,2,6]})
book = openpyxl.load_workbook('examples/ex1.xlsx') #Already existing workbook
writer = pd.ExcelWriter('examples/ex1.xlsx', engine='openpyxl') #Using openpyxl

#Migrating the already existing worksheets to writer
writer.book = book
writer.sheets = {x.title: x for x in book.worksheets}

df1.to_excel(writer, sheet_name='sheet4')
writer.save()

Hope this works for you.

Answer 2

openpyxl has support for Pandas dataframes so you're best off using it directly. See http://openpyxl.readthedocs.io/en/latest/pandas.html for more details.

Answer 3

Here is a helper function:

def append_df_to_excel(filename, df, sheet_name='Sheet1', startrow=None,
                       truncate_sheet=False, 
                       **to_excel_kwargs):
    """
    Append a DataFrame [df] to existing Excel file [filename]
    into [sheet_name] Sheet.
    If [filename] doesn't exist, then this function will create it.

    Parameters:
      filename : File path or existing ExcelWriter
                 (Example: '/path/to/file.xlsx')
      df : dataframe to save to workbook
      sheet_name : Name of sheet which will contain DataFrame.
                   (default: 'Sheet1')
      startrow : upper left cell row to dump data frame.
                 Per default (startrow=None) calculate the last row
                 in the existing DF and write to the next row...
      truncate_sheet : truncate (remove and recreate) [sheet_name]
                       before writing DataFrame to Excel file
      to_excel_kwargs : arguments which will be passed to `DataFrame.to_excel()`
                        [can be dictionary]

    Returns: None
    """
    from openpyxl import load_workbook

    # ignore [engine] parameter if it was passed
    if 'engine' in to_excel_kwargs:
        to_excel_kwargs.pop('engine')

    writer = pd.ExcelWriter(filename, engine='openpyxl')

    try:
        # try to open an existing workbook
        writer.book = load_workbook(filename)

        # get the last row in the existing Excel sheet
        # if it was not specified explicitly
        if startrow is None and sheet_name in writer.book.sheetnames:
            startrow = writer.book[sheet_name].max_row

        # truncate sheet
        if truncate_sheet and sheet_name in writer.book.sheetnames:
            # index of [sheet_name] sheet
            idx = writer.book.sheetnames.index(sheet_name)
            # remove [sheet_name]
            writer.book.remove(writer.book.worksheets[idx])
            # create an empty sheet [sheet_name] using old index
            writer.book.create_sheet(sheet_name, idx)

        # copy existing sheets
        writer.sheets = {ws.title:ws for ws in writer.book.worksheets}
    except FileNotFoundError:
        # file does not exist yet, we will create it
        pass

    if startrow is None:
        startrow = 0

    # write out the new sheet
    df.to_excel(writer, sheet_name, startrow=startrow, **to_excel_kwargs)

    # save the workbook
    writer.save()

Usage:

append_df_to_excel('test.xlsx', df, sheet_name="Sheet3", startcol=0, startrow=20)

Some details:

**to_excel_kwargs - used in order to pass additional named parameters to df.to_excel() like i did in the example above - parameter startcol is unknown to append_df_to_excel() so it will be treated as a part of **to_excel_kwargs parameter (dictionary).

writer.sheets = {ws.title:ws for ws in writer.book.worksheets} is used in order to copy existing sheets to writer openpyxl object. I can't explain why it's not done automatically when reading writer = pd.ExcelWriter(filename, engine='openpyxl') - you should ask authors of openpyxl module about that...