Python - save loop output

Question

I would need help saving the values my for-loop iterates over.

With this script I create my csv the way I need it, but there is no information what value w and c has in each row. How can I add this information in two more columns?

import pandas as pd

df = pd.read_csv(...)

country_list = df.Country.unique()
wave_list = df.Wave.unique()

dn = pd.DataFrame()

for w in wave_list:
    print ("Wave is: " + str(w))
    wave_select =df[df["Wave"] == w] # Select Rows for Waves
    for c in country_list:
        print ("Country is: " + str(c))
        country_select = df[df["Country"] == c] # Select Rows for Countries
        out = country_select["Sea"].value_counts(normalize=True)*100 # Calculate Percentage
        print (out)
        dn = dn.append(out)
dn.to_csv (...)

I would be very grateful for help.

Please add some example input data and add the expected result to make it easier to help you — D-E-N
– D-E-N, Commented Nov 22, 2020 at 11:43

I.P. · Accepted Answer · 2020-11-22 11:50:03Z

2

Before loop: dn = pd.DataFrame(columns=['wave','country','out'])

Inside inner loop instead of dn = dn.append(out):

dn = dn.append({'wave':w,'country':c,'out':out}, ignore_index=True)

answered Nov 22, 2020 at 11:50

I.P.

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4 Comments

Aditya Over a year ago

Should be the expected answer

Thessla7 Over a year ago

Thank you, that is exactly what I was looking for! :)

Thessla7 Over a year ago

As I look at the saved csv I still see something is wrong. Only the last set of calculation is stored. I have the same results for all waves.

I.P. Over a year ago

The inner loop makes exactly the same calculations for every wave. Maybe you should use wave_select in the inner loop.

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