change value in pandas dataframe using iteration

Question

I have a training data set of the following format:

print(data.head(5))
#Output



           0  1
0  a b c d e  1
1  a b c d e  1
2  a b c d e  1
3  a b c d e  1
4  a b c d e  1

It is a text classification task and I am trying to split the text "a b c d e" in to a Python list. I tried iteration:

data #the dataset
len_data = len(data)
for row_num in range(len_data):
    data.loc[row_num, 0] = data.loc[row_num, 0].split(" ")

However this doesn't work and returned the error Must have equal len keys and value when setting with an iterable. Could someone help me with this problem? Many thanks!