change_number.py

def change_number(number):
    number = number.replace(',','')

    #handling it as an error
    try:
        int(number)
        print(number)
    except Exception:
        print('None')


    #using .isdigit()
    if number.isdigit():
        print(number)
    else:
        print('None')

change_number('123,123')