Python Database

Question

My question is how to create a simple database in python. My example is:

User = {
'Name' : {'Firstname', 'Lastname'},
'Address' : {'Street','Zip','State'},
'CreditCard' : {'CCtype','CCnumber'},
}

Now I can update this User's information just fine, but how do I

1. Add more users to this data structure. A dictionary of dictionaries?
2. Allow users to have more than one credit card, a many to one relationship

Thanks for any responses, I've been trying to wrap my head around this for awhile

• Mike DeSimone: The real trouble is that this in-memory approach gets messy fast. If you have a dictionary of users, what do you use for the keys? What if there are duplicate keys? etc.
• kojiro: By the way, you may be interested in this Python-related list of databases, particularly the native Python ones.

Answer 1

You might be interested in SQLAlchemy. It makes an actual database, such as SQLite or MySQL, work more like Python classes.

Answer 2

Most key-value stores I've seen are either a dictionary of dictionaries (like mongo*) or a dictionary of strings (like redis). There are pros and cons to both approaches. I don't know what you want, so I'll give the simplest answer: Go with a list of dictionaries:

Users = []
Users.append({
 'Name' : {'Firstname', 'Lastname'}, # Are these sets?
 'Address' : {'Street','Zip','State'},
 'CreditCard' : {'CCtype','CCnumber'},
})

*OK, to be fair, Mongo is more like a dictionary of magic strings. It's json, but the lookups are handled internally, so you can treat it like a dictionary of arbitrary (but json-serializable) data structures.

Answer 3

You can create a simple database in Python with sqlite, here's a basic tutorial for it.

• Dylan Pierce: I'm sure that would be much easier, but my prof is somewhat of a prick and wants us to learn the hard way

Answer 4

​1. Add more users to this data structure. A dictionary of dictionaries?

A list of dictionaries.

[{'name': ...}, {'name': ...}]

​ 2. Allow users to have more than one credit card, a many to one relationship

A list.

{'name': ..., 'creditcard': [['type', 'number'], ['type', 'number']]}

• Dylan Pierce: Oh great, thank you, I just need to find a way to create users based off this structure. Thank you

Answer 5

Create a User class to store the information. The class can have a creditcards attribute which is a list of CreditCard class instances that get added to class instances either when they're created or later using a class method you can define. Other methods can update this (and other) attributes as necessary when called. It's called object-oriented programming (OOP).

Instances can be stored in memory within instances of a variety of built-in container classes such as lists and dicts. They can be stored onto disk and retrieved later using the pickle, shelve, json, and sqlite3 modules, just to name a few.

You're not trying to do anything that hasn't been done before -- which is good news because it means there's lot of off-the-shelf software at your disposal, but you'll have to read up on them in the documentation and probably ask a few more questions until you've learned how to use them, then you can start answering questions. ;-)

Welcome to Python!