Can I add a new colum to a data frame with only one value assigned to a specifc row and the other rows be a different value?

Question

I would like to add a column to my data frame and assign the first row value for that column a specific number...every other row would be na or 0 for the time being until changed later on.

Answer 1

Code-

import pandas as pd

data={'email':['xyz@xyz.com','xyz1@xyz.com','xyz2@xyz.com','xyz3@xyz.com'],'Difference':[15,23,45,23],'Mean':[14,26,42,29]}

df=pd.DataFrame(data)

# df['buy'] = df.iloc[0, df.columns.get_loc('buy')] = "x"
#Create new col with NAN values
df["new_col"] = np.nan #or " " 
df.iloc[0, df.columns.get_loc('new_col')] = 1 #assign value to 1st row
df #print the dataframe

Output-

            email       Mean    new_col
0       xyz@xyz.com     15      1.0
1       xyz1@xyz.com    23      NaN
2       xyz2@xyz.com    45      NaN
3       xyz3@xyz.com    23      NaN

Ref link-https://stackoverflow.com/questions/31569384/set-value-for-particular-cell-in-pandas-dataframe-with-iloc