How do I add a column to an existing excel file using python?

Question

here is my code:

import openpyxl, pprint
wb = openpyxl.load_workbook('/Users/sarahporgess/Desktop/SSA1.xlsx')
sheet = wb.get_sheet_by_name('Sheet1')


data = {}
for row in range(1,sheet.max_row+1):


        date = sheet['A' +str(row)].value
        gamma = sheet['B' +str(row)].value
        theta = sheet['C' +str(row)].value
        ratio = float(gamma)/float(theta)
        resultFile = open('SSA2.csv' , 'w')
        resultFile.write( pprint.pformat(date))
        resultFile.write( pprint.pformat(gamma))
        resultFile.write( pprint.pformat(theta))

        resultFile.write( pprint.pformat(ratio))
        print(ratio)
        sheet['D1']=ratio
resultFile.close()
print('Done.')

my existing excel file currently has three columns: "date, gamma, theta". I want to add a fourth column called "ratio" that is the ratio of gamma/theta. How do I add another column to an existing excel document using python? This code creates an excel document with the 4 elements printed into one cell

Answer 1

It is easier to use the Pandas package

import pandas as pd
file_name = #Path to your file
df = pd.read_excel(file_name) #Read Excel file as a DataFrame

df['Ratio'] = df['Gamma']/df['Theta']
#Display top 5 rows to check if everything looks good
df.head(5)

#To save it back as Excel
df.to_excel("path to save") #Write DateFrame back as Excel file

Answer 2

From your updated question I have rewrote my answer.

You don't need to use another library to accomplish what you are trying to do. Here is another option for accomplishing what you want.

import openpyxl
import pprint

wb = openpyxl.load_workbook('/Users/sarahporgess/Desktop/SSA1.xlsx')
sheet = wb.active
# you may also use the wb.get_sheet_by_name('Sheet1') method here.


data = {}
for row in range(1,sheet.max_row+1):
        date = sheet.cell(row = row, column = 1) # use .cell() to get values of cells
        gamma = sheet.cell(row = row, column = 2)
        theta = sheet.cell(row = row, column = 3)
        print(date, gamma, theta)
        ratio = float(gamma)/float(theta)
        new_wb = openpyxl.Workbook() # creates new workbook to be saved as results
        # you can also open a wookbook here instead but I wrote it to create a results workbook as I didnt already have one.
        new_sheet = new_wb.active
        new_sheet['A1'] = pprint.pformat(date)
        new_sheet['B1'] = pprint.pformat(gamma)
        new_sheet['C1'] = pprint.pformat(theta)
        new_sheet['D1'] = pprint.pformat(ratio)
        print(ratio)
        # save new workbook as SSA2
        new_wb.save('/Users/sarahporgess/Desktop/SSA2.xlsx')

print('Done.')

Answer 3

It's not clear from your code whether you want to print the result or edit the existing file. If you're editing an Excel file then you might want to create a formula and let Excel do the calculation for you.

import openpyxl
wb = openpyxl.load_workbook('/Users/sarahporgess/Desktop/SSA1.xlsx')
sheet = wb['Sheet1']

for row in sheet:
     date, gamma, theta = row
     ratio = theta.offset(column=1)
     ratio.value = "=B{0}/C{0}".format(theta.row) # if you want the formula
     # ratio.value = gamma/theta # if you just want the calculation

wb.save(…)