cf.Comparison

class cf.Comparison(**kwargs)

Bases: object

Create an object for storing a comparison expression.

A comparison expression comprises a relation (such as ‘less than’) and a value (any object capable of being related to with the standard comparison operators). These are stored in the relation and value attributes respectively.

The comparison is evaluated for an arbitrary object with the evaluate method.

Valid relations are:

Relation	Description
lt	Strictly less than
le	Less than or equal
gt	Strictly greater than
ge	Greater than or equal
eq	Equals (within a tolerance)
ne	Not equal to (within a tolerance)
inside	Inside a given range (range bounds included)
outside	Outside a given range (range bounds excluded)

See also

As a convenience, for each relation in the above list there is an identically named function which returns the appropriate Comparison object.

Parameters:**kwargs –

A keyword argument to the call is the relation of the comparison (any one of the relations listed above). The keyword’s argument is the object to test the comparison against. If the keyword argument is “inside” or “outside” then the value should be a two-element list or tuple.

Special attributes:

Attribute	Description
relation	A string definging the comparison operator. One of relations given above.
value	The object with which to compare.

Examples:

>>> c = cf.Comparison(le = 5)
>>> c.evaluate(4)
True
>>> c.evaluate(5)
True

>>> c = lt(5)
>>> c.evaluate(4)
True

>>> c = cf.Comparison(inside = (1,2))
>>> a = numpy.arange(4)
>>> c.evaluate(a)
array([False,  True,  True, False], dtype=bool)
>>> (a >= 1) & (a <= 2)
array([False,  True,  True, False], dtype=bool)

Methods and attributes defined here:

dump(id=None, omit=())

Return a string containing a full description of the object.

Parameters:

• id (str) – Optional. Set the common prefix of component names. If None then defaults to the class name.
• omit (sequence) – Optional. Omit the given attributes from the description.

Returns:

A string containing the description.

See also

cf.dump

evaluate(x)

Evaluate the comparison for a given object.

Parameters:x (object) – An object. Returns:Typically a boolean or array of booleans. More generally, the output from the appropriate relation operators (==, !=, <, >, <=, >=) for the given variable, x.

Examples:

>>> c = cf.Comparison(lt = 5.5)
>>> c.evaluate(6)
False

>>> c = cf.Comparison(inside = (1,2))
>>> array = numpy.arange(4)
>>> c.evaluate(array)
array([False,  True,  True, False], dtype=bool)