bw2data.query

Module Contents

Classes

Dictionaries	Pretends to be a single dictionary when applying a Query to multiple databases.
Filter	A filter on a dataset.
Query	A container for a set of filters applied to a dataset.
Result	A container that wraps a filtered dataset. Returned by a calling a Query object. A result object functions like a read-only dictionary; you can call Result[some_key], or some_key in Result, or len(Result).

Functions

NF(value)	Shortcut for a name filter
PF(value)	Shortcut for a reference product filter
try_op(f, x, y)

Attributes

operators

class bw2data.query.Dictionaries(*args)

Pretends to be a single dictionary when applying a Query to multiple databases.

Usage:

first_database = Database(…).load() second_database = Database(…).load() my_joined_dataset = Dictionaries(first_database, second_database) search_results = Query(filter_1, filter_2)(my_joined_dataset)

items()

class bw2data.query.Filter(key, function, value)

A filter on a dataset.

The following functions are supported:

• “<”, “<=”, “==”, “>”, “>=”: Mathematical relations

• “is”, “not”: Identity relations. Work on any Python object.

• “in”, “notin”: List or string relations.

• “iin”, “iis”, “inot”: Case-insensitive string relations.

• “len”: Length relation.

In addition, any function which defines a relationship between an input and an output can also be used.

Examples:

• All name values are “foo”: Filter("name", "is", "foo")

• All name values include the string “foo”: Filter("name", "has", "foo")

• Category (a list of categories and subcategories) includes “foo”: Filter("category", "has", "foo")

Args:

• key (str): The field to filter on.

• function (str or object): One of the pre-defined filters, or a callable object.

• value (object): The value to test against.

Returns:

A Result object which wraps a new data dictionary.

class bw2data.query.Query(*filters)

A container for a set of filters applied to a dataset.

Filters are applied by calling the Query object, and passing the dataset to filter as the argument. Calling a Query with some data returns a Result object with the filtered dataset.

Args:

• filters (filters): One or more Filter objects.

add(filter_)

Add another filter.

Args:

filter_ (Filter): A Filter object.

class bw2data.query.Result(result)

A container that wraps a filtered dataset. Returned by a calling a Query object. A result object functions like a read-only dictionary; you can call Result[some_key], or some_key in Result, or len(Result).

The dataset can also be sorted, using sort(field); the underlying data is then a collections.OrderedDict.

Args:

• result (dict): The filtered dataset.

items()

items()

keys()

sort(field, reverse=False)

Sort the filtered dataset. Operates in place; does not return anything.

Args:

• field (str): The key used for sorting.

• reverse (bool, optional): Reverse normal sorting order.

bw2data.query.NF(value)

Shortcut for a name filter

bw2data.query.PF(value)

Shortcut for a reference product filter

bw2data.query.try_op(f, x, y)

bw2data.query.operators