Write values to a particular cell in a sheet in pandas in python

Question

I have an excel sheet, which already has some values in some cells.

For ex :-

        A      B      C      D
1      val1   val2          val3
2             valx   valy        

I want pandas to write to specific cells without touching any other cells,sheet etc

This is the code i tried.

import pandas as pd
from openpyxl import load_workbook

df2 = pd.DataFrame({'Data': [13, 24, 35, 46]})
book = load_workbook('b.xlsx')
writer = pd.ExcelWriter('b.xlsx', engine='openpyxl')

df2.to_excel(writer, "Sheet1", startcol=7,startrow=6)

writer.save()

However this code deletes the older cell values.

I have reffered to :- How to write to an existing excel file without overwriting data (using pandas)? but this solution does not work.

Answer 1

I was not able to do what was asked by me in the question by using pandas, but was able to solve it by using Openpyxl.

I will write few code snippets which would help in achieving what was asked.

import openpyxl

# to open the excel sheet and if it has macros
srcfile = openpyxl.load_workbook('docname.xlsx', read_only=False, keep_vba=True)

# get sheetname from the file
sheetname = srcfile.get_sheet_by_name('sheetname')
# write something in B2 cell of the supplied sheet
sheetname['B2'] = str('write something')
# write to row 1,col 1 explicitly, this type of writing is useful to
# write something in loops
sheetname.cell(row=1, column=1).value = 'something'

# save it as a new file, the original file is untouched and here I am saving
# it as xlsm(m here denotes macros).
srcfile.save('newfile.xlsm')

So Openpyxl writes to a purticular cell, without touching the other sheets,cells etc. It basically writes to a new file respecting the properties of the original file.

Answer 2

UPDATE2: appending data to existing Excel sheet, preserving other (old) sheets:

import pandas as pd
from openpyxl import load_workbook

fn = r'C:\Temp\.data\doc.xlsx'

df = pd.read_excel(fn, header=None)
df2 = pd.DataFrame({'Data': [13, 24, 35, 46]})

writer = pd.ExcelWriter(fn, engine='openpyxl')
book = load_workbook(fn)
writer.book = book
writer.sheets = dict((ws.title, ws) for ws in book.worksheets)

df.to_excel(writer, sheet_name='Sheet1', header=None, index=False)
df2.to_excel(writer, sheet_name='Sheet1', header=None, index=False,
             startcol=7,startrow=6)

writer.save()

UPDATE: your Excel file doesn't have a header, so you should process it accordingly:

In [57]: df = pd.read_excel(fn, header=None)

In [58]: df
Out[58]:
     0    1
0  abc  def
1  ghi  lmn

In [59]: df2
Out[59]:
   Data
0    13
1    24
2    35
3    46

In [60]: writer = pd.ExcelWriter(fn)

In [61]: df.to_excel(writer, header=None, index=False)

In [62]: df2.to_excel(writer, startcol=7,startrow=6, header=None, index=False)

In [63]: writer.save()

OLD answer:

You can use the following trick:

first read the existing contents of the excel file into a new DF:

In [17]: fn = r'C:\Temp\b.xlsx'

In [18]: df = pd.read_excel(fn)

In [19]: df
Out[19]:
       A      B     C      D
0   val1    NaN  val3   val4
1  val11  val22   NaN  val33

now we can write it back and append a new DF2:

In [20]: writer = pd.ExcelWriter(fn)

In [21]: df.to_excel(writer, index=False)

In [22]: df2.to_excel(writer, startcol=7,startrow=6, header=None)

In [23]: writer.save()