Append new data into existing excel file pandas python

Question

hello everyone I'm attempting to add new data (columns and values) to an already existing excel spreadsheet. I have Order_Sheet.xlsx saved with data as such:

 Item:         Quantity:      Price: 
disposable cups   7000         $0.04

and add this info from spreadsheet_1.xlsx

  Order Number    Location    Date
 0 A-21-897274     Ohio        07/01/2022

add them to the existing excel sheet Order_Sheet.xlsx instead of creating a new excel. so that it would look like:

 Item:         Quantity:      Price:   Order Number:    Location:    Date:
 disposable cups   7000         $0.04   A-21-897274      Ohio     07/01/2022

Is there an easy way to append new data to an existing excel or possibly combine two excel files?

Answer 1

Working only with pandas 1.4+. The following code assumes that the order of the row are the same between the first and the second write. It also assumes that you exactly know the number of existing columns.

import pandas as  pd


df2 = pd.DataFrame({"c": [3, 5], "d": [8, 9]})
df3 = pd.DataFrame({"c": [9, 10], "d": [-1, -9]})
df4 = pd.DataFrame({"a": [1, 2], "b": [3, 4]})

with pd.ExcelWriter('./Order_List.xlsx', mode='w') as writer:
    df2.to_excel(writer, index=False)

with pd.ExcelWriter('./Order_List.xlsx', mode="a", if_sheet_exists="overlay") as writer:
    df3.to_excel(writer, startrow=3, header=False, index=False)
    df4.to_excel(writer, startrow=0, startcol=2, header=True, index=False)

Link to the 1.4 documentation .

Answer 2

I find this in the documentation.

  {storage_options}
        .. versionadded:: 1.2.0
    if_sheet_exists : {{'error', 'new', 'replace', 'overlay'}}, default 'error'
        How to behave when trying to write to a sheet that already
        exists (append mode only).
        * error: raise a ValueError.
        * new: Create a new sheet, with a name determined by the engine.
        * replace: Delete the contents of the sheet before writing to it.
        * overlay: Write contents to the existing sheet without removing the old
          contents.
        .. versionadded:: 1.3.0

Here is the full link: https://github.com/pandas-dev/pandas/blob/main/pandas/io/excel/_base.py#L800-L814