How does one populate a row in pandas python

Question

I have initialised a dataframe in python to simulate a matrix

 llist = ["this", "is", "a","sentence"]
 df = pd.DataFrame(columns = llist, index = llist)

Now I want to populate a row as follows

 test = [1,0,0,0]
 df.iloc[[1]] = test

this throws up the following error

ValueError: cannot set using a list-like indexer with a different length than the value

When I set the value as below it populates the row with the same value

  test = [1]
  df.iloc[[1]] = test

Can someone tell me why this happens and the most efficient way of populating a row with a list of different values?

Answer 1

I think you need remove one [] :

test = [1,0,0,0]
df.iloc[1] = test

print (df) 
         this   is    a sentence
this      NaN  NaN  NaN      NaN
is          1    0    0        0
a         NaN  NaN  NaN      NaN
sentence  NaN  NaN  NaN      NaN