Replace values of list knowing its index and value in Pandas DataFrame

Question

I have this 3 lists on a Pandas DF:

            flat_values                          indexes                  tmp_values
[20, None, None, None, None, 30, 40]           [1, 2, 3, 4]            [40, 30, 10, 10]

What I want to do is to get a new field on my DF with a list consisting of the flat_values list and the tmp_values inserted at the position reflected in the indexes list numbers. So that:

               flat_values                          indexes                  tmp_values         new_values 
    [20, None, None, None, None, 30, 40]           [1, 2, 3, 4]            [40, 30, 10, 10]    [20, 40, 30, 10, 10, 30, 40]

Thank you very much

What do you mean with index position? Both 20 for flat_values and 40 for tmp_values are position 0. — Celius Stingher
– Celius Stingher, Commented Jan 9, 2020 at 11:17
Done. I mean, for example, value 40 of tmp_values in position 1 (first value of indexes list) of flat_values list. Indexes and tmp_values lists always have the same length. — FranG91
– FranG91, Commented Jan 9, 2020 at 11:27

E. Zeytinci · Accepted Answer · 2020-01-09 11:41:16Z

1

You can use apply,

def replace_val(row):
    l = row['flat_values'].copy()

    for i, m in zip(row['indexes'], row['tmp_values']):
        l[i] = m

    return l

df['new_values'] = df.apply(replace_val, axis=1)

Here is example,

a = [20, None, None, None, None, 30, 40]
b = [1, 2, 3, 4]
c = [40, 30, 10, 10]

d = [20, None, None, 30, 40]
e = [1, 2]
f = [100, 120]

df = pd.DataFrame({'flat_values': [a, d], 'indexes': [b, e], 'tmp_values': [c, f]})

def replace_val(row):
    l = row['flat_values'].copy()

    for i, m in zip(row['indexes'], row['tmp_values']):
        l[i] = m

    return l

df['new_values'] = df.apply(replace_val, axis=1)
print(df)

                            flat_values       indexes        tmp_values  \
0  [20, None, None, None, None, 30, 40]  [1, 2, 3, 4]  [40, 30, 10, 10]
1              [20, None, None, 30, 40]        [1, 2]        [100, 120]

                     new_values
0  [20, 40, 30, 10, 10, 30, 40]
1        [20, 100, 120, 30, 40]

edited Jan 9, 2020 at 11:41

answered Jan 9, 2020 at 11:29

E. Zeytinci

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1 Comment

E. Zeytinci Over a year ago

Thanks for confirmation. I added copy() to the function because it also changes the values of flat_values. Maybe you want to change it. @FranG91

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