Create a pandas column using for loop

# importing libraries
import pandas as pd
import numpy as np
raw_Data = {'Voter_name': ['Geek1', 'Geek2', 'Geek3', 'Geek4', 
                           'Geek5', 'Geek6', 'Geek7', 'Geek8'], 
            'Voter_age': [15, 23, 25, 9, 67, 54, 42, np.NaN]}
df = pd.DataFrame(raw_Data, columns = ['Voter_name', 'Voter_age'])
#       //DataFrame will look like
#
# Voter_name          Voter_age
# Geek1                15
# Geek2                23
# Geek3                25
# Geek4                09
# Geek5                67
# Geek6                54
# Geek7                42
# Geek8           not a number
eligible = []
# For each row in the column
for age in df['Voter_age']:       
    if age >= 18:                   # if Voter eligible
        eligible.append('Yes')
    elif age < 18:                  # if voter is not eligible
        eligible.append("No")
    else:
        eligible.append("Not Sure")
# Create a column from the list
df['Voter'] = eligible  
          
print(df)