how to change values in a df specifying by index contain in multiple lists, and each list for one column

Question

I have a list where I have all the index of values to be replaced. I have to change them in 8 diferent columns with 8 diferent lists. The replacement could be a simple string. How can I do it? I have more than 20 diferent columns in this df

Eg:

list1 = [0,1,2]
list2 =[2,4]
list8 = ...

sustitution = 'no data'

Column A	Column B
marcos	peter
Julila	mike
Fran	Ramon
Pedri	Gavi
Olmo	Torres

OUTPUT: 

| Column A | Column B |
| -------- | -------- |
| no data  | peter    |
| no data  | mike     |
| no data  | no data  |
| Pedri    | Gavi     |
| Olmo     | no data  |`

jezrael · Accepted Answer · 2022-11-24 08:11:03Z

1

Use DataFrame.loc with zipped lists and columns names:

list1 = [0,1,2]
list2 =[2,4]

L = [list1,list2]
cols = ['Column A','Column B']

sustitution = 'no data'

for c, i in zip(cols, L):
    df.loc[i, c] = sustitution
print (df)
  Column A Column B
0  no data    peter
1  no data     mike
2  no data  no data
3    Pedri     Gavi
4     Olmo  no data

edited Nov 24, 2022 at 8:11

answered Nov 24, 2022 at 7:45

jezrael

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4 Comments

D EA Over a year ago

Thank you for your answer but appears: ValueError: too many values to unpack (expected 2)

jezrael Over a year ago

@DEA - It was copy error, need for c, i in zip(df.columns, L): instead for c, i in L

D EA Over a year ago

Thanks, now is executing without error, but do not change values properly. Notice that df have more than 8 columns but I only want to change this specific 8

jezrael Over a year ago

@DEA - I change solution by this requirement, you can check it here

mozway · Accepted Answer · 2022-11-24 07:55:47Z

0

You can use the underlying numpy array:

list1 = [0,1,2]
list2 = [2,4]

lists = [list1, list2]

col = np.repeat(np.arange(len(lists)), list(map(len, lists)))
# array([0, 0, 0, 1, 1])
row = np.concatenate(lists)
# array([0, 1, 2, 2, 4])

df.values[row, col] = 'no data'

Output:

  Column A Column B
0  no data    peter
1  no data     mike
2  no data  no data
3    Pedri     Gavi
4     Olmo  no data

answered Nov 24, 2022 at 7:55

mozway

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