Update: Added more clarifications
Steps:
1) Read the sheet which needs changes in a dataframe and make changes in that dataframe.
2) Now the changes are reflected in the dataframe but not in the sheet. Use the following function with the dataframe in step 1 and name of the sheet to be modified. You will use the truncate_sheet param to completely replace the sheet of concern.
The function call would be like so:
append_df_to_excel(filename, df, sheet_name, startrow=0, truncate_sheet=True)
from openpyxl import load_workbook
import pandas as pd
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
"""
# ignore [engine] parameter if it was passed
if "engine" in to_excel_kwargs:
to_excel_kwargs.pop("engine")
writer = pd.ExcelWriter(filename, engine="openpyxl")
# Python 2.x: define [FileNotFoundError] exception if it doesn"t exist
try:
FileNotFoundError
except NameError:
FileNotFoundError = IOError
if "index" not in to_excel_kwargs:
to_excel_kwargs["index"] = False
try:
# try to open an existing workbook
if "header" not in to_excel_kwargs:
to_excel_kwargs["header"] = True
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
to_excel_kwargs["header"] = False
# 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
to_excel_kwargs["header"] = True
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()
We can't replace openpyxl engine here to write excel files as asked in comment. Refer reference 2.
References:
1) https://stackoverflow.com/a/38075046/6741053
2) xlsxwriter: is there a way to open an existing worksheet in my workbook?
