Converting Dictionary¶
At the moment, the only class contained in this model 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)]
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: 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
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class
sage.misc.converting_dict.
KeyConvertingDict
(key_conversion_function, data=None)¶ 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
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has_key
(key)¶ Deprecated; present just for the sake of compatibility.
Use
key in self
instead.INPUT:
key
– A value identifying the element, will be converted.
EXAMPLES:
sage: from sage.misc.converting_dict import KeyConvertingDict sage: d = KeyConvertingDict(int) sage: d[3] = 42 sage: d.has_key("3") doctest:warning...: DeprecationWarning: use 'key in dictionary' syntax instead See https://trac.sagemath.org/25281 for details. True sage: d.has_key(4) False
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pop
(key, *args)¶ 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: ...
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setdefault
(key, default=None)¶ 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)]
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update
(*args, **kwds)¶ 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}