py-app-properties 0.2.0

Java application properties for Python

Python Application Properties

How To Use

The main purpose of this library is to simplify work with an application configs.

Let's assume that you have some email service which requires a couple message templates. It'll look like:

class EmailService:
    CONFIRM_REGISTRATION_TEMPLATE = "Thanks for your registration!"
    RESET_PASSWORD_TEMPLATE = "To reset a password follow the link - {link}"
    # and another templates...
    
    def __init__(self, mail_sender: IMailSender) -> None:
        self._sender = mail_sender
    
    def send_confirm_registration_mail(self, username: str) -> None:
        self._sender.send_mail(username, self.CONFIRM_REGISTRATION_TEMPLATE)
    
    def send_reset_password_email(self, username: str, link: str) -> None:
        template = self.RESET_PASSWORD_TEMPLATE.format(link=link)
        self._sender.send_mail(username, template)
    # and another methods...

As you can see, there are some problems connected with storing message templates in class variables:

• Templates could have a big size and that decrease readability of a whole class.
• It's also hard to maintain different versions of templates.

But if you have config file my_config.yml with content below, you can "inject" variables to the EmailService class:

email_templates:
  confirm_registration_template: Thanks for your registration!
  reset_password_template: To reset a password follow the link - {link}
  # and so on...

@properties(filename="my_config.yml", root="email_templates")
class EmailService:
    CONFIRM_REGISTRATION_TEMPLATE: str
    RESET_PASSWORD_TEMPLATE: str
    # and another templates...
    
    def __init__(self, mail_sender: IMailSender) -> None:
        self._sender = mail_sender
    
    def send_confirm_registration_mail(self, username: str) -> None:
        self._sender.send_mail(username, self.CONFIRM_REGISTRATION_TEMPLATE)
    
    def send_reset_password_email(self, username: str, link: str) -> None:
        template = self.RESET_PASSWORD_TEMPLATE.format(link=link)
        self._sender.send_mail(username, template)
    # and another methods...

And that's all. Just one decorator and some file with application properties. You can even inject all necessary data into dataclass object:

@properties(filename="my_config.yml", root="email_templates")
@dataclass(init=False)
class EmailTemplates:
    confirm_registration_template: str
    reset_password_template: str

init=False is required if you don't want to pass and override params during instance initialization.

Available features

• Supporting .yaml and .json extensions of configs.
• Accessing nested configs using root variable:

# "config.yaml"
some:
  very:
    nested:
      variable:
        key: value

@propeties(filename="config.yaml", root="some.very.nested.variable")
class Config:
    key: str

• Overriding default values with override_default=True
• Type casting for primitive types. Nested types will be added soon.
• Case ignoring by default is true. You can switch off this option.