Calculate and add column in python

Question

I think I have a fairly simple question for a python expert. With a lot of struggling I put together underneath code. I am opening an excel file, transforming it to a list of lists and adding a column to this list of lists. Now I want to rename and recalculate the rows of this added column. How do I script that I always take the last column of a list of lists, even though the number of columns could differ.

import xlrd
file_location = "path"
workbook = xlrd.open_workbook(file_location)
sheet = workbook.sheet_by_index(0)
data = [[sheet.cell_value(r, c) for c in range(sheet.ncols)] for r in range(sheet.nrows)]
data = [x + [0] for x in data]

What do you mean by adding a column to a list of lists? Do you mean you add an element to the inner list? — user707650
– user707650, Commented Dec 22, 2014 at 9:40
I got it from here: stackoverflow.com/questions/2002415/… He calls it adding a column. Not sure if that is exactly what I do but it appears to be what I want. — Zuenie
– Zuenie, Commented Dec 22, 2014 at 9:41

babbageclunk · Accepted Answer · 2014-12-22 09:44:00Z

1

If you have a function called calculate_value that takes a row and returns the value for that row, you could do it like this:

def calculate_value(row):
    # calculate it...
    return value

def add_calculated_column(rows, func):
    result_rows = []
    for row in rows:
        # create a new row to avoid changing the old data
        new_row = row + [func(row)]
        result_rows.append(new_row)
    return result_rows

data_with_column = add_calculated_column(data, calculate_value)

answered Dec 22, 2014 at 9:44

babbageclunk

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2 Comments

Zuenie Over a year ago

This looks like what I want. Thank you. Going to test it now.

Zuenie Over a year ago

Ok. This has helped a lot already. I am capable of recalculating a value in the last column. However, I want my first row to have a different value than the second row of the column. The first row being integer and the second row being a calculated value.

Zuenie · Accepted Answer · 2014-12-22 10:48:31Z

0

I found a more easy and more flexible way of adjusting the values in the last column.

counter = 0
for list in data:
    counter = counter + 1
    if counter == 1:
        value = 'Vrspng'
    else:
        value = counter
    list.append(value)

answered Dec 22, 2014 at 10:48

Zuenie

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