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A DSL to build Lucene text queries in Python.

Project description

synopsis:A Python DSL for Lucene queries.

Easily create Lucene query strings without having to learn the language itself. The syntax is simple to use and allows creating larger queries from multiple smaller ones. A basic lesson on proper Lucene queries can be found here.

Supports Python 2.6+.

Getting Started

>>> from lucenequerybuilder import Q

Creating Queries

A basic query can be given by passing in a string into Q’s constructor.

>>> q = Q('a')
>>> q = Q('The quick brown fox')

The query builder will automatically detect whether a term (no whitespace) or a phrase (multiple terms together seaparated by whitespace) and properly bound them with quotation marks.

All terms and phrases are expected to be unescaped, and will be escaped:

>>> q = Q(r'The *quick* brown (fox)')

>>> str(q)

'"The \\*quick\\* brown \\(fox\\)"'

Range Queries

Ranges are also easy to put into a query. There are two types of range queries, inclusive range and exclusive range. These are passed into the query builder with keyword arguments.

>>> q = Q(inrange=(1,5))
>>> q = Q(exrange=['egg','hgg'])

Ranges will work with any list-like object of length 2.

Chaining Queries

You can chain queries with & (AND), | (OR), & ~ (AND NOT), + (MUST), and - (MUST NOT). AND, OR, and AND NOT require a query before and after it shows up. MUST and MUST NOT only work on the query directly afterwards. Some examples are below:

>>> q = Q('a') & Q('b')

>>> q = Q('a') & ~Q('b')

>>> q = +Q('a') -Q('b')

Nested Queries

Queries can be nested inside of each other to create new queries. This makes it easy to group queries together. Examples below:

>>> q = Q(Q('a') & Q('b')) & ~Q('c')

>>> q = Q(Q(Q('a') | Q(inrange=[1,2])) +Q('c))


Fields can be added to queries by putting in a field as your first argument. Fields cannot have any whitespace and cannot be nested inside each other. The following examples are valid queries:

>>> q = Q('name', 'Edward')

>>> q = Q('text', 'Mary had a little lamb')

>>> q = Q('age', inrange=[10, 9001])

The following examples are invalid queries which will raise an error:

>>> q = Q('name', Q('lastname', 'Purcell'))

>>> q = Q('bad', Q('range', inrange=[10, 9001]))

Fuzzy Queries

A fuzzy term query can be accomplished using the fuzzy keyword:

>>> q = Q('name', fuzzy=('edd', .2))

>>> str(q)


The first element in the fuzzy tuple is the term, and the second is the similarity ratio- a float, str, or decimal between 0 and 1.

If you drop the second element, and just provide a str, the string will signify to use Lucene’s default ratio - 0.5:

>>> q = Q('name', fuzzy='edd')

>>> str(q)


Wildcard Queries

To keep wildcard queries from having ‘?’ and ‘*’ from being escaped, simple include the wildcard flag:

>>> str(Q('c?t', wildcard=True))


which will match ‘cat’ or ‘cot’.

Boosting & Wildcard Queries

These queries are not yet supported, but will be soon. Feel free to add support yourself and request a pull!

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