Sum the values of a column with Python

Question

I'm new to python, I would like to read a column of values from a csv file and add them together, but only those to the left of the "," My csv File:

Name     Code  
Angel    19;90
Eduardo  20;21
Miguel   30;45

I would like to be able to sum only the numbers to the left of the "Code" column, so that my output is "19+20+30 = 69". I tried deleting the ";" and converting the string to int but sums but joins the numbers together and I have this output:

Your final sum is : 1990 +2021 +3045 = 7056

expected ouput is 69 ? Or 7056 ?

jezrael
– jezrael

2023-01-31 11:37:47 +00:00
Commented Jan 31, 2023 at 11:37 — jezrael
– jezrael, Commented Jan 31, 2023 at 11:37
output is 69, @jezrael

Jacket
– Jacket

2023-01-31 11:54:59 +00:00
Commented Jan 31, 2023 at 11:54 — Jacket
– Jacket, Commented Jan 31, 2023 at 11:54

jezrael · Accepted Answer · 2023-01-31 12:00:19Z

5

If need sum values before ; use Series.str.extract with casting to integers and then sum:

out = df['Code'].str.extract('(.*);', expand=False).astype('int').sum()

Or use Series.str.split with select first values of lists by str[0]:

out = df['Code'].str.split(';').str[0].astype('int').sum()

If need sum all values create DataFrame by expand=True and summing first per rows and then Series:

out = df['Code'].str.split(';', expand=True).astype('int').sum().sum()

If need sum without ; use Series.str.replace:

out = df['Code'].str.replace(';','', regex=True).astype('int').sum()

edited Jan 31, 2023 at 12:00

answered Jan 31, 2023 at 11:34

jezrael

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Comments

Zsolt Balint · Accepted Answer · 2023-01-31 11:41:00Z

2

You can do this like that:

import csv

sum = 0
with open("data.csv", "r") as file:
    reader = csv.reader(file)
    next(reader) # skip header row
    for row in reader:
        code_values = row[1].split(";")
        for value in code_values:
            sum += int(value)

print(sum)

In line with "split" you can do any kind of splitting logic.

answered Jan 31, 2023 at 11:41

Zsolt Balint

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1 Comment

Jacket Over a year ago

I tried this code but it gives me the following error :IndexError: list index out of range

S M · Accepted Answer · 2023-01-31 13:41:07Z

1

Just modified ZsoltB's answer :

import csv

sum = 0
with open("demo.csv", "r") as file:
    reader = csv.reader(file)
    next(reader) # skip header row
    for row in reader:
        code_values = row[1].split(";")
        print(code_values[0])
        sum += int(code_values[0])

print(sum)

The code_values[0] will ensure that you add values only from the left column.

answered Jan 31, 2023 at 13:41

S M

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4 Comments

Jacket Over a year ago

This code takes the data by row, I need it to add by column

S M Over a year ago

You want to add 19 + 20 + 30 right ?

Jacket Over a year ago

yes, yep, correct

S M Over a year ago

The above code does the same. I created a demo.csv file and it worked.

Timeless · Accepted Answer · 2023-01-31 12:06:28Z

0

Since it's a calculation thing, here is an approach with numpy :

import numpy as np

d = {"left": 0, "right": 1}
choice = "left" # <- choose the position here

arr = np.genfromtxt("jacket.csv", delimiter=",", # <- specify a sep
                     dtype=None, skip_header=1, encoding=None)

left_vals = np.array([int(code.split(";")[d[choice]]) for code in arr[:,1]])

out = np.sum(left_vals)

Output :

print(out)
#69

answered Jan 31, 2023 at 12:06

Timeless

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2 Comments

Jacket Over a year ago

Hi @Timeless, i try your code and i have this error : IndexError: too many indices for array: array is 1-dimensional, but 2 were indexed

Timeless Over a year ago

AFK now, let me check that later ;). Anyways, for the sample you shared, the code should work.

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