Create an empty object of a specified type dynamically

Question

Using a dataclass to specify a set of environment variables and am trying to keep the dataclass separate from a class that modifies the environment. Passing in an instance of the dataclass and have a get_env that determines if those variables are set in the environment. When os.getenv(field.name.upper(), None) is called I want None to be type as specified in the dataclass. e.g. if field.type is a str I want something like os.getenv(field.name.upper(), field.type.__new__(field.type))

This seems to work but would like to confirm this makes sense or what alternatives to consider?

class Env:
  def __init__(self, config: Config):
    self.config = config

  def get_env_dict(self):
    return self.config.to_dict()

  def get_env(self):
    env_dict = self.get_env_dict()
    for field in fields(self.config):
      env_dict[field.name.upper()] = os.getenv(field.name.upper(), None)

score 0 · Answer 1 · answered Jul 20 '22 at 12:29

This works for a dataclass with strings. unsure yet if it will work will all kinds of types.

class Env:
  def __init__(self, config: Config):
    self.config = config

  def get_env_dict(self):
    return self.config.to_dict()

  def get_env(self):
    env_dict = self.get_env_dict()
    for field in fields(self.config):
      env_dict[field.name.upper()] = os.getenv(
                                               field.name.upper(), 
                                               field.type.__new__(field.type)
                                              )

Create an empty object of a specified type dynamically

1 Answers1