liquer 0.0.4

Query your objects for two cents!

Query your objects for two cents with Django like Q objects.

Some Examples

Q objects help you identify an object if its any attribute conforms your custom predicate dsl. Let’s take a look at the example below:

from liquer import Q


class MyClass:
    def __init__(self, foo):
        self.foo = foo

# Define a query.
# We expect foo attribute of an object to be 'bar'
# regardless of case sensivity
q = Q(foo__iexact='bar')

# Create one MyClass instance
my_obj = MyClass(foo='Bar')

# Test my_obj if it conforms our query object
assert q(my_obj)  # Evaluates to True

# We are also free to test any dictionary object
my_dict = {'foo': 'Bar'}
assert q(my_dict)

# Let's fail a test
my_fail_obj = MyClass(foo='Baz')
assert q(my_fail_obj)  # Evaluates to False, Throws assertion error

You can tail more attributes using ‘__’ underscores to digg objects:

>>> from liquer import Q
>>> my_dict = {'foo': {'bar': {'baz': 1}}}
>>> q = Q(foo__bar__baz__lte=2)

>>> q(my_dict)
True

Also there is chance for applying and/or logics to query couples:

>>> q = Q(foo__bar__gt=0) & Q(foo__bar__lt=9)  # The same as Q(foo__bar__gt=0, foo__bar__lt=9)
>>> q({'foo': {'bar': 5}})
True
>>> q({'foo': {'bar': 18}})
False

Let’s try or logic:

>>> q = Q(foo__bar=3) | Q(foo__bar=5)
>>> q({'foo': {'bar': 3}})
True
>>> q({'foo': {'bar': 5}})
True
>>> q({'foo': {'bar': 4}})
False

It’s very useful in most cases to register a callback when querying objects:

>>> q = Q(foo__bar=3) | Q(foo__bar=5)
>>> q.callback({'foo': {'bar': 3}}, lambda x: 'bar found %s' % x['foo']['bar'])
'bar found 3'

The funniest part is to register your own predicates:

>>> from liquer import Q, register
>>> register('is_sqrt', lambda x, y: x / y == y)
>>> q = Q(foo__is_sqrt=5)
>>> q({'foo': 25})
True

More is coming soon…

Enjoy!

Licence

Copyright (c) 2012 Kadir Pekel.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.