Converting Dictionary

At the moment, the only class contained in this module is a key converting dictionary, which applies some function (e.g. type conversion function) to all arguments used as keys.

AUTHORS:

  • Martin von Gagern (2015-01-31): initial version

EXAMPLES:

A KeyConvertingDict will apply a conversion function to all method arguments which are keys:

sage: from sage.misc.converting_dict import KeyConvertingDict
sage: d = KeyConvertingDict(int)
sage: d["3"] = 42
sage: list(d.items())
[(3, 42)]

>>> from sage.all import *
>>> from sage.misc.converting_dict import KeyConvertingDict
>>> d = KeyConvertingDict(int)
>>> d["3"] = Integer(42)
>>> list(d.items())
[(3, 42)]

This is used e.g. in the result of a variety, to allow access to the result no matter how a generator is identified:

sage: # needs sage.libs.singular sage.rings.number_field
sage: K.<x,y> = QQ[]
sage: I = ideal([x^2 + 2*y - 5, x + y + 3])
sage: V = sorted(I.variety(AA), key=str)
sage: v = V[0]
sage: v['x'], v['y']
(-2.464101615137755?, -0.535898384862246?)
sage: list(v)[0].parent()
Multivariate Polynomial Ring in x, y over Algebraic Real Field

>>> from sage.all import *
>>> # needs sage.libs.singular sage.rings.number_field
>>> K = QQ['x, y']; (x, y,) = K._first_ngens(2)
>>> I = ideal([x**Integer(2) + Integer(2)*y - Integer(5), x + y + Integer(3)])
>>> V = sorted(I.variety(AA), key=str)
>>> v = V[Integer(0)]
>>> v['x'], v['y']
(-2.464101615137755?, -0.535898384862246?)
>>> list(v)[Integer(0)].parent()
Multivariate Polynomial Ring in x, y over Algebraic Real Field
class sage.misc.converting_dict.KeyConvertingDict(key_conversion_function, data=None)[source]

Bases: dict

A dictionary which automatically applies a conversions to its keys.

The most common application is the case where the conversion function is the object representing some category, so that key conversion means a type conversion to adapt keys to that category. This allows different representations for keys which in turn makes accessing the correct element easier.

INPUT:

  • key_conversion_function – a function which will be applied to all method arguments which represent keys

  • data – (optional) dictionary or sequence of key-value pairs to initialize this mapping

EXAMPLES:

sage: from sage.misc.converting_dict import KeyConvertingDict
sage: d = KeyConvertingDict(int)
sage: d["3"] = 42
sage: list(d.items())
[(3, 42)]
sage: d[5.0] = 64
sage: d["05"]
64

>>> from sage.all import *
>>> from sage.misc.converting_dict import KeyConvertingDict
>>> d = KeyConvertingDict(int)
>>> d["3"] = Integer(42)
>>> list(d.items())
[(3, 42)]
>>> d[RealNumber('5.0')] = Integer(64)
>>> d["05"]
64
pop(key, *args)[source]

Remove and retrieve a given element from the dictionary.

INPUT:

  • key – a value identifying the element, will be converted

  • default – the value to return if the element is not mapped, optional

EXAMPLES:

sage: from sage.misc.converting_dict import KeyConvertingDict
sage: d = KeyConvertingDict(int)
sage: d[3] = 42
sage: d.pop("3")
42
sage: d.pop("3", 33)
33
sage: d.pop("3")
Traceback (most recent call last):
...
KeyError: ...

>>> from sage.all import *
>>> from sage.misc.converting_dict import KeyConvertingDict
>>> d = KeyConvertingDict(int)
>>> d[Integer(3)] = Integer(42)
>>> d.pop("3")
42
>>> d.pop("3", Integer(33))
33
>>> d.pop("3")
Traceback (most recent call last):
...
KeyError: ...
setdefault(key, default=None)[source]

Create a given mapping unless there already exists a mapping for that key.

INPUT:

  • key – a value identifying the element, will be converted

  • default – the value to associate with the key

EXAMPLES:

sage: from sage.misc.converting_dict import KeyConvertingDict
sage: d = KeyConvertingDict(int)
sage: d.setdefault("3")
sage: list(d.items())
[(3, None)]

>>> from sage.all import *
>>> from sage.misc.converting_dict import KeyConvertingDict
>>> d = KeyConvertingDict(int)
>>> d.setdefault("3")
>>> list(d.items())
[(3, None)]
update(*args, **kwds)[source]

Update the dictionary with key-value pairs from another dictionary, sequence of key-value pairs, or keyword arguments.

INPUT:

  • key – a value identifying the element, will be converted

  • args – a single dict or sequence of pairs

  • kwds – named elements require that the conversion function accept strings

EXAMPLES:

sage: from sage.misc.converting_dict import KeyConvertingDict
sage: d = KeyConvertingDict(int)
sage: d.update([("3",1),(4,2)])
sage: d[3]
1
sage: d.update({"5": 7, "9": 12})
sage: d[9]
12
sage: d = KeyConvertingDict(QQ['x'])
sage: d.update(x=42)
sage: d
{x: 42}

>>> from sage.all import *
>>> from sage.misc.converting_dict import KeyConvertingDict
>>> d = KeyConvertingDict(int)
>>> d.update([("3",Integer(1)),(Integer(4),Integer(2))])
>>> d[Integer(3)]
1
>>> d.update({"5": Integer(7), "9": Integer(12)})
>>> d[Integer(9)]
12
>>> d = KeyConvertingDict(QQ['x'])
>>> d.update(x=Integer(42))
>>> d
{x: 42}