Everyone I know who has a dog has a partner or family member who can help them look after their pet. With dogs, there is a strong need to look after their exercise, their meals, and their general well-being. With cats however, they are relatively lower maintenance.
I am personally a dog person but I would say that if you are living alone, having a dog is not very practical. This definitely becomes more of an issue once you become a clerk in the hospital and have long and odd hours. Someone will need to take the dog out for their walk or for their “number one” and “number two” needs.
Hope that answers your question!