reltools 0.1.0

Relation tools for Python.

Relation tools for Python. This relates two data (sorted by certain keys) like SQL joining.

Inspired by itertools.groupby, as long as input data are sorted, almost all processes are evaluated lazily, which results in the reduction of memory usage. This feature is for the big data joining without any SQL engines.

Installation

Choose one from the following.

• Install with pip.

  • Run pip install reltools.

• Put reltools.py into your project.

Samples

First, import reltools.

>>> from reltools import relate_one_to_many

Here, input data are sorted in 1st and 2nd keys.

>>> lhs = [
...     (1, 'a', 's'),
...     (2, 'a', 't'),
...     (3, 'b', 'u'),
... ]
>>> rhs = [
...     (1, 'a', 'v'),
...     (1, 'b', 'w'),
...     (3, 'b', 'x'),
... ]

One-To-Many

Here is a sample for one-to-many relations.

>>> one_to_many_related = relate_one_to_many(lhs, rhs)
>>> for left, right in one_to_many_related:
...     left, list(right)
((1, 'a', 's'), [(1, 'a', 'v'), (1, 'b', 'w')])
((2, 'a', 't'), [])
((3, 'b', 'u'), [(3, 'b', 'x')])

You can use custom keys for all API functions.

>>> import operator
>>> custom_key = operator.itemgetter(0, 1)
>>> one_to_many_related = relate_one_to_many(
...     lhs, rhs, lhs_key=custom_key, rhs_key=custom_key)
>>> for left, right in one_to_many_related:
...     left, list(right)
((1, 'a', 's'), [(1, 'a', 'v')])
((2, 'a', 't'), [])
((3, 'b', 'u'), [(3, 'b', 'x')])

License

Copyright (c) 2018 Yu MOCHIZUKI