You can use pd.DataFrame.loc
to add a row to your dataframe:
iname = "name1"
ipassword = "password1"
iemail = "email@domain.com"
df = pd.read_csv("login.csv", sep=',', encoding="utf-8")
df.loc[df.index.max()+1] = [iname, ipassword, iemail]
df.to_csv("login.csv", index=False)