Adding extra n rows at the end of a dataframe of a certain value

I have a dataframe with currently 22 rows

index value
  0     23
  1     22
  2     19
 ...
 21     20

to this dataframe, i want to add 72 rows to make the dataframe exactly 100 rows. So i need to fill loc[22:99] but with a certain value, let’s say 100.

I tried something like this

uncon_dstn_2021['balance'].loc[22:99] = 100

but did not work. Any idea?

>Solution :

You can do reindex

out = df.reindex(df.index.tolist() + list(range(22, 99+1)), fill_value = 100)