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Declare and load configuration from environment variables

Project description

Declare and load configuration from environment variables.

Install

pip install config

Examples

Declare and load scalar values

from config import Config, parse_int, parse_float, parse_str, parse_bool

cfg = Config()

# declare variables with the appropriate parser
cfg.declare('my_int_variable', parse_int())
cfg.declare('my_float_variable', parse_float())
cfg.declare('my_str_variable', parse_str())
cfg.declare('my_bool_variable', parse_bool())

# load the values

# will load the value of MY_INT_VARIABLE as an int
int_result = cfg.get('my_int_variable')
# will load the value of MY_FLOAT_VARIABLE as a float
float_result  = cfg.get('my_float_variable')
# will load the value of MY_STR_VARIABLE as a str
str_result = cfg.get('my_str_variable')

Declare and load list values

from config import Config, parse_int_list

cfg = Config()

# declare variables with the appropriate parser
cfg.declare('my_int_list_variable', parse_int_list())

# load the values

# will load the value of MY_INT_LIST_VARIABLE as a list of ints.
# By default it assumes the elements to be comma separated
int_list_result = cfg.get('my_int_list_variable')

Declare and load nested values

from config import Config, parse_str

cfg = Config()
cfg.declare(
    'dict',
    {
       'value1': parse_str(),
       'dict2': {
           'value2': parse_str(),
       },
    },
)

# this will load values from two environment variables DICT_VALUE_1 and DICT_DICT2_VALUE2 and return them in the
# same structure as declared above
dict_result = cfg.get('dict')

Add validation

from config import Config, parse_str, parse_str_list
from validators import email

# config expects validators to raise an Error on failure.
# Since the validators package returns Failures instead of raising, we create a small adapter.
def email_validator(value):
    result = email(value)
    if isinstance(result, ValidationFailure):
        raise ValueError('"{}" is not a valid email address'.format(value))

cfg = Config()

cfg.declare('valid_email', parse_str(validator=email_validator))
# this also works with lists. The validator function is applied to each value separately
cfg.declare('valid_list_of_emails, parse_str_list(validator=email_validator))

valid_email = cfg.get('valid_email')
valid_list_of_emails = cfg.get('valid_list_of_emails')

Reloading configuration at runtime

from config import Config, parse_str, reload

cfg = Config()
cfg.declare('some_value', parse_str())
value = cfg.get('some_value')

# Values are actually loaded during declare().
# Changes to the environment at runtime are not picked up automatically.
# Relaoding has to be triggered explicitly.

cfg.reload()

new_value = cfg.get('some_value')

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