py-app-properties 0.3.0

Java application properties for Python

Python Application Properties

What is this

This is a simple library to inject non-sensitive configurations like message templates, dictionaries, and lists with required settings into class variables.

How to install

To install this library just enter:

pip intall py-app-properties

How To Use

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

Let's assume that you have some email service that requires a couple of message templates (it could be also a dictionary with default HTTP headers and other kinds of mappings). It'll look like this:

class EmailService:
    CONFIRM_REGISTRATION_TEMPLATE = "Thanks for your registration!"
    RESET_PASSWORD_TEMPLATE = "To reset a password follow the link - {link}"
    # and other 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 other 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 decreases the 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 the 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 other 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 other methods...

And that's all. Just one decorator and a 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.

About contributing

You will make this library better if you open issues or create pull requests with improvements here. Also, you can write me directly in a private message if you have some questions or recommendations.