Loading collections

The core of Invoke’s execution model involves one or more Collection objects. While these may be created programmatically, in typical use Invoke will create them for you from Python modules it finds or is told to use.

Task module discovery

With no other configuration, simply calling invoke will look for a single Python module or package named tasks, and will treat it as the root namespace. tasks (or any other name given via loading configuration options) is searched for in the following ways:

  • First, if a valid tasks module by that name already exists on Python’s sys.path, no more searching is done – that module is selected.

  • Failing that, search towards the root of the local filesystem, starting with the user’s current working directory (os.getcwd) and try importing again with each directory temporarily added to sys.path.

    • Due to how Python’s import machinery works, this approach will always favor a package directory (tasks/ containing an __init__.py) over a module file (tasks.py) in the same location.
    • If a candidate is found and successfully imported, its parent directory will stay on sys.path during the rest of the Python session – this allows task code to make convenient assumptions concerning sibling modules’ importability.

Candidate modules/packages are introspected to make sure they can actually be used as valid task collections. Any that fail are discarded, the sys.path munging done to import them is reverted, and the search continues.

Configuring the loading process

You can configure the above behavior, requesting that Invoke alter the collection name searched for and/or the path where filesystem-level loading starts looking.

For example, you may already have a project-level tasks.py that you can’t easily rename; or you may want to host a number of tasks collections stored outside the project root and make it easy to switch between them; or any number of reasons.

Both the sought collection name and the search root can be specified via configuration file options or as runtime CLI flags:

  • Change the collection name: Set the tasks.collection_name configuration option, or use the -c/--collection CLI flag. It should be a Python module name and not a file name (so mytasks, not mytasks.py or mytasks/.)
  • Change the root search path: Configure tasks.search_root or use -r/--root. This value may be any valid directory path.