Python in-memory ORM database
Project description
littletable - a Python module to give ORM-like access to a collection of objects
The littletable module provides a low-overhead, schema-less, in-memory database access to a collection
of user objects. littletable provides a DataObject class for ad hoc creation of semi-immutable objects
that can be stored in a littletable Table. Tables can also contain user-defined objects, using those
objects' __dict__, __slots__, or _fields mappings to access object attributes.
In addition to basic ORM-style insert/remove/query/delete access to the contents of a Table, littletable offers:
- simple indexing for improved retrieval performance, and optional enforcing key uniqueness
- access to objects using indexed attributes
- simplified joins using '+' operator syntax between annotated Tables
- the result of any query or join is a new first-class littletable Table
littletable Tables do not require an upfront schema definition, but simply work off of the attributes in the stored values, and those referenced in any query parameters.
Here is a simple littletable data storage/retrieval example:
from littletable import Table, DataObject
customers = Table('customers')
customers.create_index("id", unique=True)
customers.insert(DataObject(id="0010", name="George Jetson"))
customers.insert(DataObject(id="0020", name="Wile E. Coyote"))
customers.insert(DataObject(id="0030", name="Jonny Quest"))
catalog = Table('catalog')
catalog.create_index("sku", unique=True)
catalog.insert(DataObject(sku="ANVIL-001", descr="1000lb anvil", unitofmeas="EA",unitprice=100))
catalog.insert(DataObject(sku="BRDSD-001", descr="Bird seed", unitofmeas="LB",unitprice=3))
catalog.insert(DataObject(sku="MAGNT-001", descr="Magnet", unitofmeas="EA",unitprice=8))
catalog.insert(DataObject(sku="MAGLS-001", descr="Magnifying glass", unitofmeas="EA",unitprice=12))
wishitems = Table('wishitems')
wishitems.create_index("custid")
wishitems.create_index("sku")
# easy to import CSV data from a string or file
wishitems.csv_import("""\
custid,sku
0020,ANVIL-001
0020,BRDSD-001
0020,MAGNT-001
0030,MAGNT-001
0030,MAGLS-001
""")
# print a particular customer name
# (unique indexes will return a single item; non-unique
# indexes will return a list of all matching items)
print(customers.by.id["0030"].name)
# print all items sold by the pound
for item in catalog.where(unitofmeas="LB"):
print(item.sku, item.descr)
# print all items that cost more than 10
for item in catalog.where(lambda o: o.unitprice>10):
print(item.sku, item.descr, item.unitprice)
# join tables to create queryable wishlists collection
wishlists = customers.join_on("id") + wishitems.join_on("custid") + catalog.join_on("sku")
# print all wishlist items with price > 10
bigticketitems = wishlists().where(lambda ob: ob.unitprice > 10)
for item in bigticketitems:
print(item)
# list all wishlist items in descending order by price
for item in wishlists().sort("unitprice desc"):
print(item)
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