poisk 1.0.3

Small utilities for searching data structures

Poisk implements a thin veneer of convenience over familiar search functions. It can be used for:

• regular expression searches;
• jq- or JMESPath-style searches in lists and dicts;
• XPath queries over ElementTrees.

one and many

At the core of Poisk is the idea that you'd rather raise an exception than extract the wrong data. We want to check that our expectations hold. If we expect our search to return matches, it should not return an empty list. If we expect a single matching element, there shouldn't be two.

The search functions are grouped into two modules, called one and many. The search functions under one expect to find a single matching value, which they return. They raise NotFound if no results are found, and ManyFound if more than one match is found.

Here is an example using one.re, which performs regular expression searches:

>>> from poisk import one

>>> one.re(r'H\w+', 'Hello world!')
'Hello'

>>> one.re(r'H\w+', 'Greetings, world!')
Traceback (most recent call last):
    ...
poisk.exceptions.NotFound: 'H\\w+' in 'Greetings, world!'

>>> one.re(r'H\w+', 'Ho Ho Ho, world!')
Traceback (most recent call last):
    ...
poisk.exceptions.ManyFound: 'H\\w+' in 'Ho Ho Ho, world!'

The corresponding functions under many expect one or more results, which they return as a list. They raise NotFound if no matches are found:

>>> from poisk import many

>>> many.re(r'\w+', 'Hello!')
['Hello']

>>> many.re(r'\w+', 'Hello world!')
['Hello', 'world']

>>> many.re(r'\d+', 'Hello world!')
Traceback (most recent call last):
    ...
poisk.exceptions.NotFound: '\\d+' in 'Hello world!'

Supported search functions

The previous two examples use one.re and many.re to perform regular expression searches, using the standard re module.

Also available are functions for xpath search over ElementTrees using lxml.etree:

>>> import lxml.etree as ET
>>> from poisk import many, one

>>> document = ET.HTML('''
...     <div>
...         <p id="p1">First paragraph</p>
...         <p id="p2">Second paragraph</p>
...     </div>
... ''')

>>> one.etree('p[@id="p1"]/text()', document)
'First paragraph'

>>> many.etree('p/text()', document)
['First paragraph', 'Second paragraph']

The same one.etree and many.etree functions accept CSS selectors (via cssselect):

>>> one.etree('p#p1', document).text
'First paragraph'

The one.pods and many.pods functions allow searches using Plain Old Data Structures (dicts and lists) using a jq- or JMESPath-style query language:

>>> data = {
...     "payload": {
...         "total": 3,
...         "results": [
...             {"id": 1},
...             {"id": 2},
...             {"id": 3},
...         ],
...     },
... }

>>> one.pods('payload.total', data)
3

>>> many.pods('payload.results[].id', data)
[1, 2, 3]

The test/ directory contains many more examples of the sort functionality that Poisk offers.