Python: How to replace once csv file column with another csv file column?

Question

I have two csv files as follows:

one.csv

date time temperature, humidity
01-01-2017,20:45:00,100, 2.1
01-01-2017,21:00:00,100, 2.2
01-01-2017,21:15:00,100,2.3
01-01-2017,21:30:00,100, 2.4
01-01-2017,21:45:00,100, 2.5
01-01-2017,22:00:00,100, 2.6

two.csv

date time temperature
01-01-2017,20:45:00,50
01-01-2017,21:00:00,70
01-01-2017,21:15:00,40
01-01-2017,21:30:00,30
01-01-2017,21:45:00,100
01-01-2017,22:00:00,20

I want to replace values of temperature of one.csv with two.csv based on date and time so the expected output file will be like this:

output.csv
date time temperature, humidity
01-01-2017,20:45:00,50, 2.1
01-01-2017,21:00:00,70, 2.2
01-01-2017,21:15:00,40,2.3
01-01-2017,21:30:00,30, 2.4
01-01-2017,21:45:00,100, 2.5
01-01-2017,22:00:00,20, 2.6

Any help would be highly appreciated. Sorry I am very beginner for python. Thanks

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Chris Marotta
– Chris Marotta

2021-04-21 13:39:31 +00:00
Commented Apr 21, 2021 at 13:39 — Chris Marotta
– Chris Marotta, Commented Apr 21, 2021 at 13:39
Consider using pandas

Sebastien D
– Sebastien D

2021-04-21 13:40:23 +00:00
Commented Apr 21, 2021 at 13:40 — Sebastien D
– Sebastien D, Commented Apr 21, 2021 at 13:40

Sebastien D · Accepted Answer · 2021-04-26 11:24:33Z

1

Pandas might help you with that:

import pandas as pd
df1 = pd.read_csv('one.csv')
df2 = pd.read_csv('two.csv')
df_out = df1[['date','time','humidity']].merge(df2[['date','time','temperature']],on=['date','time'])
df_out.to_csv('out.csv',index=False)

Output

    date    time    temperature humidity
01-01-2017  20:45:00    50  2.1
01-01-2017  21:00:00    70  2.2
01-01-2017  21:15:00    40  2.3
01-01-2017  21:30:00    30  2.4
01-01-2017  21:45:00    100 2.5
01-01-2017  22:00:00    20  2.6

edited Apr 26, 2021 at 11:24

answered Apr 21, 2021 at 13:46

Sebastien D

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1 Comment

user2778724 Over a year ago

It gives an error KeyError: "['humidity'] not in index"

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