Source code for sceptre.resolvers.sub

from sceptre.resolvers import Resolver

[docs]class Sub(Resolver): """This resolver allows you to create a string using Python string format syntax. This is a great way to combine together a number of resolver outputs into a single string. This functions very similarly to Cloudformation's ``!Sub`` intrinsic function. The argument to this resolver should be a two-element list: (1) Is the format string, using curly-brace templates to indicate variables, and (2) a dictionary where the keys are the format string's variable names and the values are the variable values. Example: parameters: ConnectionString: !sub - "postgres://{username}:{password}@{hostname}:{port}/{database}" - username: {{ var.username }} password: !ssm /my/ssm/password hostname: !stack_output my/database/stack.yaml::HostName port: !stack_output my/database/stack.yaml::Port database: {{var.database}} """
[docs] def resolve(self): error_message = ( "The argument to !sub must be a two-element list, where the first element is the " "a format string and the second element is a dict of values to interpolate into it." ) if not isinstance(self.argument, list) or len(self.argument) != 2: self.raise_invalid_argument_error(error_message) template, variables = self.argument if not isinstance(template, str) or not isinstance(variables, dict): self.raise_invalid_argument_error(error_message) try: return template.format(**variables) except KeyError as e: self.raise_invalid_argument_error( f"Could not find !sub argument for {e}", e )