runway.lookups.handlers.base module

Base class for lookup handlers.

class runway.lookups.handlers.base.LookupHandler[source]

Bases: object

Base class for lookup handlers.

classmethod dependencies(_LookupHandler__lookup_query: VariableValue)Set[str][source]

Calculate any dependencies required to perform this lookup.

Note that lookup_query may not be (completely) resolved at this time.

classmethod format_results(value: Any, get: Optional[str] = None, load: Optional[str] = None, transform: Optional[str] = None, **kwargs: Any)Any[source]

Format results to be returned by a lookup.

  • value – Data collected by the Lookup.

  • get – Nested value to get from a dictionary like object.

  • load – Parser to use to parse a formatted string before the get and transform method.

  • transform – Convert the final value to a different data type before returning it.


TypeError – If get is provided but the value value is not a dictionary like object.

Runs the following actions in order:

  1. load() if load is provided.

  2. runway.util.MutableMap.find() or dict.get() depending on the data type if get is provided.

  3. transform() if transform is provided.

classmethod handle(_LookupHandler__value: str, context: Union[CfnginContext, RunwayContext], *_LookupHandler__args: Any, provider: Optional[Provider] = None, **_LookupHandler__kwargs: Any)Any[source]

Perform the lookup.

  • __value – Parameter(s) given to the lookup.

  • context – The current context object.

  • provider – CFNgin AWS provider.

classmethod parse(value: str)Tuple[str, Dict[str, str]][source]

Parse the value passed to a lookup in a standardized way.


value – The raw value passed to a lookup.


The lookup query and a dict of arguments

classmethod load(value: Any, parser: Optional[str] = None, **kwargs: Any)Any[source]

Load a formatted string or object into a python data type.

First action taken in format_results(). If a lookup needs to handling loading data to process it before it enters format_results(), is should use args.pop('load') to prevent the data from being loaded twice.

  • value – What is being loaded.

  • parser – Name of the parser to use.


The loaded value.

classmethod transform(value: Any, *, to_type: Optional[str] = 'str', **kwargs: Any)Any[source]

Transform the result of a lookup into another datatype.

Last action taken in format_results(). If a lookup needs to handling transforming the data in a way that the base class can’t support it should overwrite this method of the base class to register different transform methods.

  • value – What is to be transformed.

  • to_type – The type the value will be transformed into.


The transformed value.