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 named tasks, and will treat it as the root namespace. tasks (and any other module name given via the load 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.

Additional load options

The -c / --collection command-line argument allows you to override the default collection name searched for. It should be a Python module name and not a file name (so -c mytasks, not -c mytasks.py or -c mytasks/.) This option is repeatable and may be used to load multiple collections at runtime.

Note

When multiple collections are specified, the first collection given will be used as the root or default namespace. The rest will be attached to it as sub-collections. See Constructing namespaces for details.

If you need to override the default search start point so Invoke no longer searches from the current directory, use --root. E.g. if your tasks module is in /opt/code/myproject/tasks.py and your CWD is, say, /home/myuser, you might run Invoke as:

$ invoke --root /opt/code/myproject