Create new column with incremental values efficiently

Question

I am creating a column with incremental values and then appending a string at the start of the column. When used on large data this is very slow. Please suggest a faster and eff

Answer 1

One possible solution is with convert values to strings by map:

df['New_Column'] = np.arange(len(df['a']))+1
df['New_Column'] = 'str_' + df['New_Column'].map(str)