Appending Pandas DataFrame to existing Excel document

Question

Per https://github.com/pandas-dev/pandas/pull/21251/files/09e5b456e1af5cde55f18f903ab90c761643b05a, we should be able to append DataFrames to new XLSX sheets.

Based

Answer 1

You can use with:

with pd.ExcelWriter('test.xlsx', engine='openpyxl', mode='a') as writer:
    d1.to_excel(writer,sheet_name='d1')
    d2.to_excel(writer,sheet_name='d2')
    writer.save()

writer.close()

update

This should work just note that the a blank file needs to be created before hand. You can just create a blank file using python if you want. I created a simple loop to, in some ways, mimic the essence of what you are trying to accomplish:

import pandas as pd
from openpyxl import load_workbook

d1 = pd.DataFrame({"A":['Bob','Joe', 'Mark'], 
               "B":['5', '10', '20']})
d2 = pd.DataFrame({"A":['Jeffrey','Ann', 'Sue'], 
                "B":['1', '2', '3']})

dfs = [d1,d2]

for i in range(len(dfs)):
    sheet = 'd'+str(i+1)
    data = dfs[i]
    writer = pd.ExcelWriter('atest.xlsx',engine='openpyxl', mode='a')
    writer.book = load_workbook('atest.xlsx') # here is the difference
    data.to_excel(writer,sheet_name=sheet)
    writer.save()
    writer.close()

or here is the modified first example:

d1 = pd.DataFrame({"A":['Bob','Joe', 'Mark'], 
               "B":['5', '10', '20']})
d2 = pd.DataFrame({"A":['Jeffrey','Ann', 'Sue'], 
                "B":['1', '2', '3']})

writer = pd.ExcelWriter('atest.xlsx', engine='openpyxl', mode='w')
d1.to_excel(writer,sheet_name='d1')
writer.save()
writer.close()

writer = pd.ExcelWriter('atest.xlsx', engine='openpyxl', mode='a')
writer.book = load_workbook('atest.xlsx')
d2.to_excel(writer,sheet_name='d2')
writer.save()
writer.close()

Answer 2

I submitted a post on GitHub and received a response from the contributors (see the highlighted portion below). It turns out that this functionality won't be released until 0.24 so it is not available in 0.23.1. FYI - I downloaded the RC and successfully tried out the mode='a'option. However, there may be a bug with workbooks that do not exist; I receive FileNotFoundError: [Errno 2] No such file or directory: 'test.xlsx'.

"this feature is being released as part of 0.24 which we just issued a release candidate for over the past few days. You can try on the RC or here on master and if neither works open an issue per the contributing guide, but this wouldn't be expected to work on versions older than that"

Answer 3

import pandas as pd

writer = pd.ExcelWriter(wk_path + save_file)
# ....
# build sc_files DataFrame and save. sc_files includes
# a column called OS.

sc_file.to_excel(writer, sheet_name='test')

# build data frame of OS counts out of sc_file
counts_os = sc_file.OS.value_counts() 

# To append to 'test' sheet, use startcol=x1, startrow=y
# To append counts_OS to the end of the current 'test' sheet
y = len(sc_file)
y += 1
counts_os.to_excel(writer, sheet_name='test', 
    startcol=1, startrow=y)

# write counts_os to sheet test2 
counts_os.to_excel(writer, sheet_name='test2')
writer.save()
writer.close()