cirq.ParamResolver

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Resolves parameters to actual values.

cirq.ParamResolver(
    param_dict: 'cirq.ParamResolverOrSimilarType' = None
) -> None

Used in the notebooks

Used in the tutorials
Simulation Quantum approximate optimization algorithm for the Ising model Quantum variational algorithm Introduction to Cirq Hello, many worlds

A parameter is a variable whose value has not been determined. A ParamResolver is an object that can be used to assign values for these variables.

ParamResolvers are hashable; their param_dict must not be mutated.

Raises
TypeError if formulas are passed as keys.

Attributes
param_dict	A dictionary from the ParameterValue key (str) to its assigned value.

Methods

value_of

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value_of(
    value: Union['cirq.TParamKey', 'cirq.TParamValComplex'],
    recursive: bool = True
) -> 'cirq.TParamValComplex'

Attempt to resolve a parameter to its assigned value.

Scalars are returned without modification. Strings are resolved via the parameter dictionary with exact match only. Otherwise, strings are considered to be sympy.Symbols with the name as the input string.

A sympy.Symbol is first checked for exact match in the parameter dictionary. Otherwise, it is treated as a sympy.Basic.

A sympy.Basic is resolved using sympy substitution.

Note that passing a formula to this resolver can be slow due to the underlying sympy library. For circuits relying on quick performance, it is recommended that all formulas are flattened before-hand using cirq.flatten or other means so that formula resolution is avoided. If unable to resolve a sympy.Symbol, returns it unchanged. If unable to resolve a name, returns a sympy.Symbol with that name.

Args
value	The parameter to try to resolve.
recursive	Whether to recursively evaluate formulas.

Returns
The value of the parameter as resolved by this resolver.

Raises
RecursionError	If the ParamResolver detects a loop in recursive resolution.
sympy.SympifyError	If the resulting value cannot be interpreted.

__bool__

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__bool__() -> bool

__eq__

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__eq__(
    other
)

Return self==value.

__getitem__

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__getitem__(
    key: Union['cirq.TParamKey', 'cirq.TParamValComplex']
) -> 'cirq.TParamValComplex'

__iter__

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__iter__() -> Iterator[Union[str, sympy.Expr]]

__ne__

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__ne__(
    other
)

Return self!=value.