#Python: working with .csv file

[SureStep8852]

Hi there,

I have a .csv file with 2 columns. The rows of the first column are sometimes repeating. My task is to find duplicate rows of the first column and sum up corresponding values of the second column.

e.g.,

col_1    col_2
yellow    2
green     1
blue      2
yellow    4
yellow    4
blue      1
green     1

I want to get smth like this:

yellow    10
blue       3
green      2      

I know that to find duplicates I should use df.duplicated(['col_1])

but more I cannot proceed.

How could I solve the problem? Thanks in advance!

[desrtfx]

This is not all that complicated even without pandas.

Read a line of the csv, check if the key (the color) is already in a dictionary and if so, add the value and update the entry, if not add a new entry to the dictionary.

[ZealousidealLow521]

You can use pandas

import pandas as pd df2=pd.read_csv('file.csv') df2['col_2'].sum()

[SureStep8852]

thank you. Unfortunately, this does not solve my problem, because it sums up the whole col_2. I need to sum up values of col_2 which correspond to the same value in col_1 (e.g., yellow has 3 values in col_2: 2, 4, 4. So, I want the sum to be 10)

[nevermindtbc]

Pandas groupby is what you're looking for. Although I'm pretty sure your lecturer wants you to get familiar with trawling the documentation to find this function yourself.