biodome 2017.6.0

biodome

biodome

Controlled environments

Reading environment variables with os.environ is pretty easy, but after a while one gets pretty tired of having to cast variables to the right types and handling fallback to defaults.

This library provides a clean way read environment variables and fall back to defaults in a sane way. Typical usage looks like this:

from biodome import biodome

MY_VAR = biodome('MY_VAR', 123)

In this case, the output MY_VAR will be created from the environment variable MY_VAR:

• If the env var MY_VAR doesn’t exist, the result will be the default value of 123.

• If the env var MY_VAR does exist, and it is the same type as the default, i.e., an int, then the output, MY_VAR, will be an int.

• If the env var MY_VAR does exist, but is not convertible to the same type as the default, i.e., an int, then the result will be the default.

The key theme here is that the type of the default value is used to determine how to cast the input value. This works for the following types:

• int

• float

• str

• list

• dict

• set

• tuple

For the containers, the eval() function is used. This might be a security risk if you don’t have control over how your environment variables are set. It would be possible to add a flag to disable eval(): PRs welcome.

The default can also be a bool, i.e., True or False. In this case, the following values, and their upper- or mixed-case equivalents will be recognized as True:

['1', 'y', 'yes', 'on', 'active', 'activated', 'enabled', 'true',
't', 'ok', 'yeah']

Anything not in this list will be considered as False.