Define a column type as 'list' in Pandas

Question

I have a pandas data frame df. I want df to be composed of 3 columns : the first one is a brand name (a string), the second is a list of integers, and the third one is a list of floats. So for each brand, I have two lists, and I want to put them all in a data frame to access different lists easily based on the brand name.

I have :

count = [1,5,198,0,0,35]
brand = 'Nike'

and to put the count list into the 'count' column corresponding to 'Nike' line I tried the following :

df[df['brand']==brand].loc[0,'count'] = count
df[df['brand']==brand]['count'] == count
df[df['brand']==brand]['count'].loc[0] == count

None of these would work and I get ValueError: Must have equal len keys and value when setting with an iterable or A value is trying to be set on a copy of a slice from a DataFrame and nothing changes in df.

How can I write a list into a pandas data frame cell ?

Answer 1

It seems to me that you are building a wrong data model. The model is not in 1st normal form (1NF) and you will have many troubles using it. Please, try to use a normalized model.

   Brand     price
0  Nike     50.0
1  Nike     60.0
2  Nike     70.0
3  Puma     30.0
4  Puma     100.0

You can get any computed value from this model with ease.