Putting many python pandas dataframes to one excel worksheet

user3817518: "Please also share if there is another way to put many dataframes into excel using the built-in df.to_excel functionality !!"

Here's my attempt:

Easy way to put together a lot of dataframes on just one sheet or across multiple tabs. Let me know if this works!

-- To test, just run the sample dataframes and the second and third portion of code.

Sample dataframes

import pandas as pd
import numpy as np

# Sample dataframes    
randn = np.random.randn
df = pd.DataFrame(randn(15, 20))
df1 = pd.DataFrame(randn(10, 5))
df2 = pd.DataFrame(randn(5, 10))

Put multiple dataframes into one xlsx sheet

# funtion
def multiple_dfs(df_list, sheets, file_name, spaces):
    writer = pd.ExcelWriter(file_name,engine='xlsxwriter')   
    row = 0
    for dataframe in df_list:
        dataframe.to_excel(writer,sheet_name=sheets,startrow=row , startcol=0)   
        row = row + len(dataframe.index) + spaces + 1
    writer.save()

# list of dataframes
dfs = [df,df1,df2]

# run function
multiple_dfs(dfs, 'Validation', 'test1.xlsx', 1)

Put multiple dataframes across separate tabs/sheets

# function
def dfs_tabs(df_list, sheet_list, file_name):
    writer = pd.ExcelWriter(file_name,engine='xlsxwriter')   
    for dataframe, sheet in zip(df_list, sheet_list):
        dataframe.to_excel(writer, sheet_name=sheet, startrow=0 , startcol=0)   
    writer.save()

# list of dataframes and sheet names
dfs = [df, df1, df2]
sheets = ['df','df1','df2']    

# run function
dfs_tabs(dfs, sheets, 'multi-test.xlsx')

To create the Worksheet in advance, you need to add the created sheet to the sheets dict:

writer.sheets['Validation'] = worksheet

Using your original code:

# Creating Excel Writer Object from Pandas  
writer = pd.ExcelWriter('test.xlsx',engine='xlsxwriter')   
workbook=writer.book
worksheet=workbook.add_worksheet('Validation')
writer.sheets['Validation'] = worksheet
df.to_excel(writer,sheet_name='Validation',startrow=0 , startcol=0)   
another_df.to_excel(writer,sheet_name='Validation',startrow=20, startcol=0) 

---

Explanation

If we look at the pandas function to_excel, it uses the writer's write_cells function:

excel_writer.write_cells(formatted_cells, sheet_name, startrow=startrow, startcol=startcol)

So looking at the write_cells function for xlsxwriter:

def write_cells(self, cells, sheet_name=None, startrow=0, startcol=0):
    # Write the frame cells using xlsxwriter.
    sheet_name = self._get_sheet_name(sheet_name)
    if sheet_name in self.sheets:
        wks = self.sheets[sheet_name]
    else:
        wks = self.book.add_worksheet(sheet_name)
        self.sheets[sheet_name] = wks

Here we can see that it checks for sheet_name in self.sheets, and so it needs to be added there as well.