How to check the availability of environment variables correctly?

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I did a token check, if at least one token is missing, 'True' will not be. Now I need to deduce which variable is missing, how to do it?

PRACTICUM_TOKEN = os.getenv('PRACTICUM_TOKEN')
TELEGRAM_TOKEN = os.getenv('TELEGRAM_TOKEN')
TELEGRAM_CHAT_ID = os.getenv('TELEGRAM_CHAT_ID')


def check_tokens():
    """Checks the availability of environment variables."""
    ENV_VARS = [PRACTICUM_TOKEN, TELEGRAM_TOKEN, TELEGRAM_CHAT_ID]
    if not all(ENV_VARS):
        print('Required environment variables are missing:', ...)
    else:
        return True
environment-variables python
2 Answers

I might suggest putting these values inside a class. The check tokens method can be part of the class, and you can use __dict__ to dynamically get reference to all of the tokens you defined without having to duplicate code.

class Environment:
    def __init__(self):
        self.PRACTICUM_TOKEN = os.getenv('PRACTICUM_TOKEN')
        self.TELEGRAM_TOKEN = os.getenv('TELEGRAM_TOKEN')
        self.TELEGRAM_CHAT_ID = os.getenv('TELEGRAM_CHAT_ID')

    def check_tokens(self):
        """Checks the availability of environment variables."""
        missing_vars = [var for var, value in self.__dict__.items() if not value]
        if missing_vars:
            print('Required environment variables are missing:', *missing_vars)
            return False
        else:
            return True

print(Environment().check_tokens())
user_32805380

A minimal adaptation of your code:

PRACTICUM_TOKEN = os.getenv('PRACTICUM_TOKEN')
TELEGRAM_TOKEN = os.getenv('TELEGRAM_TOKEN')
TELEGRAM_CHAT_ID = os.getenv('TELEGRAM_CHAT_ID')

ENV_VARS = ['PRACTICUM_TOKEN', 'TELEGRAM_TOKEN', 'TELEGRAM_CHAT_ID']


def check_tokens():
    """Checks the availability of environment variables."""
    undefined_vars = set(filter(lambda v: not globals().get(v), ENV_VARS))
    if not undefined_vars:
        return True
    print(f"Required environment variables are missing: {undefined_vars}")
    return False

But I hate writing lines like FOO = bar('FOO'), so here's a more complicated approach, partly inspired by flakes answer:

class Environment:
    env_vars = ['PRACTICUM_TOKEN', 'TELEGRAM_TOKEN', 'TELEGRAM_CHAT_ID']

    def __init__(self):
        for var in self.env_vars:
            setattr(self, var, os.getenv(var))


def check_tokens(e):
    """checks the availability of environment variables."""
    undefined_vars = set(filter(lambda v: not getattr(e, v), e.env_vars))
    if not undefined_vars:
        return True
    print(f"Required environment variables are missing: {undefined_vars}")
    return False


env = Environment()
check_tokens(env)

 $ TELEGRAM_TOKEN=1 python3 envvars.py
Required environment variables are missing: {'TELEGRAM_CHAT_ID', 'PRACTICUM_TOKEN'}
user_92885800
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