Source code for

from sceptre.resolvers import Resolver

[docs]class Select(Resolver): """This resolver allows you to select a specific index from a list of items or a specific key from a dict.. This is great for combining with the ``!split`` resolver to obtain part of a string. This function works almost the same as CloudFormation's ``!Select`` intrinsic function, **except (1) you can use this with negative indexes to select with a reverse index** and (2) you can select keys from a dict. The argument for this resolver should be a list with two elements: (1) A numerical index or string key and (2) a list or dict of items to select out of. If the index is negative, it will select from the end of the list. For example, "-1" would select the last element and "-2" would select the second-to-last element. Example: parameters: # This selects the last element after you split the connection string on "/" DatabaseName: !select - -1 - !split ["/", !stack_output my/database/stack.yaml::ConnectionString] """
[docs] def resolve(self): error_message = ( "The argument to !select must be a two-element list, where the first element is the " "index or key to select with and the second element is the list or dict to select from." ) if not isinstance(self.argument, list) or len(self.argument) != 2: self.raise_invalid_argument_error(error_message) index, items = self.argument if not isinstance(items, (dict, list)): self.raise_invalid_argument_error(error_message) try: return items[index] except (TypeError, KeyError, IndexError) as e: self.raise_invalid_argument_error( f"Could not select with index/key {index}: {e}", e )