How Can I Append a Pandas DataFrame to an Existing Excel Sheet in Python Without Overwriting?

Append Existing Excel Sheet with New Dataframe Using Python Pandas

Problem:

You have an existing Excel file and a Pandas DataFrame. You want to append the DataFrame to the end of the existing Excel sheet without overwriting it.

Solution:

There are two main approaches to append data to an existing Excel sheet using Pandas:

Approach 1: Using ExcelWriter

import pandas as pd

df = pd.DataFrame(...)

with pd.ExcelWriter('existing_sheet.xlsx', mode='a', engine='openpyxl') as writer:
    df.to_excel(writer, sheet_name='Sheet1', header=False, index=False, startrow=writer.sheets['Sheet1'].max_row + 1)

Approach 2: Using Openpyxl and Pandas

import pandas as pd
from openpyxl import load_workbook

df = pd.DataFrame(...)

# Load existing Excel workbook
book = load_workbook('existing_sheet.xlsx')
sheet = book['Sheet1']

# Find last row in existing Excel sheet
last_row = sheet.max_row

# Append DataFrame data to existing sheet starting from last row + 1
pd.DataFrame.to_excel(df, book, sheet_name='Sheet1', startrow=last_row + 1, index=False)

# Save changes to existing Excel file
book.save('existing_sheet.xlsx')

Additional Tips:

• If the sheet doesn't exist, Pandas will automatically create it.
• You can specify the start row for appending data using the startrow parameter.
• To preserve existing cell styles, set with_style=True in the copy_excel_cell_range function when using the Openpyxl and Pandas approach.
• For Pandas versions < 1.4.0, use the helper function in the linked code example to append data without overwriting.

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