env.py

'''
This script parses environment variables and gets set of three variables at the time.

It then calls function with those arguments (database, username, password) based on pattern:
    DB_<UNIQUENAME>_DATABASE
    DB_<UNIQUENAME>_USERNAME
    DB_<UNIQUENAME>_PASSWORD
'''

import re

# mimics environment variables
ENVS = {
    'DB_X_USERNAME': 'x-username',
    'DB_X_PASSWORD': 'x-password',
    'DB_X_DATABASE': 'x-database',
    'DB_Y_USERNAME': 'y-username',
    'DB_Y_PASSWORD': 'y-password',
    'DB_Y_DATABASE': 'y-database',
    'TEMP': 'some random value',
    'DBNAME': 'should not include'
}

def get_uniqe_names(envs):
    '''Creates a set of unique names from environment variables based on regex.'''
    name_set = set()
    pattern = r'^DB_[A-Z]+_DATABASE'
    for key in envs.keys():
        if re.search(pattern, key):
            name_set.add(key.split('_')[1])
    return name_set

def main():
    '''Call a function if three variables are found from environment variables'''
    for name in get_uniqe_names(ENVS):
        database = ENVS.get(f'DB_{name}_DATABASE')
        username = ENVS.get(f'DB_{name}_USERNAME')
        password = ENVS.get(f'DB_{name}_PASSWORD')
        if all((database, username, password)):
            print('calling function with:', database, username, password)

if __name__ == '__main__':
    main()