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

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" which is the gamma / theta ratio. How can I add another column to an existing excel document using python? This code creates an excel document with 4 items printed in one cell

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3 answers


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
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From your updated question, I rewrote my answer.

You don't need to use another library to accomplish what you are trying to do. Here's another option for doing 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.')
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It is not clear from your code whether you want to print the result or edit an existing file. If you are editing an Excel file, you may need 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(…)
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