import

Ansible allows unchecked imports of some libraries from specific directories. Importing any other Python library requires handling import errors. This enables support for sanity tests such as validate-modules and provides better error messages to the user.

Important

Please see the frequently asked questions for answers to common questions about resolving errors reported by this test.

Handling import errors

Ansible executes across many hosts and can use multiple Python interpreters at the same time, which may even have different versions. To ensure users get an actionable and easy to understand error we try to ensure any non-core imports in modules/plugins are guarded to avoid a traceback, which most users won’t be able to understand, much less use to solve the issue.

Another reason Ansible does this is to import the code for inspection. This allows Ansible to easily test, document, configure, etc based on the code without having to install any and all requirements everywhere, especially when that is not the context in which you execute the code.

The code below shows examples of how to avoid errors on import and then use the provided missing_required_lib to ensure the user knows which LIBRARY is missing, on which HOST it is missing and the specific INTERPRETER that requires it.

In modules

Instead of using import another_library:

import traceback

from ansible.module_utils.basic import missing_required_lib

try:
    import another_library
except ImportError:
    HAS_ANOTHER_LIBRARY = False
    ANOTHER_LIBRARY_IMPORT_ERROR = traceback.format_exc()
else:
    HAS_ANOTHER_LIBRARY = True
    ANOTHER_LIBRARY_IMPORT_ERROR = None

Note

The missing_required_lib import above will be used below.

Then in the module code, normally inside the main method:

module = AnsibleModule(...)

if not HAS_ANOTHER_LIBRARY:
    module.fail_json(
        msg=missing_required_lib('another_library'),
        exception=ANOTHER_LIBRARY_IMPORT_ERROR)

In plugins

Instead of using import another_library:

try:
    import another_library
except ImportError as imp_exc:
    ANOTHER_LIBRARY_IMPORT_ERROR = imp_exc
else:
    ANOTHER_LIBRARY_IMPORT_ERROR = None

Then in the plugin code, for example in the run method of the plugin (some plugins don’t have a run method and will require it in the __init__ method instead):

if ANOTHER_LIBRARY_IMPORT_ERROR:
    raise AnsibleError('another_library must be installed to use this plugin') from ANOTHER_LIBRARY_IMPORT_ERROR

When used as base classes

Important

This solution builds on the previous two examples. Make sure to pick the appropriate one before continuing with this solution.

Sometimes an import is used in a base class, for example:

from another_library import UsefulThing

class CustomThing(UsefulThing):
    pass

One option is make the entire class definition conditional:

if not ANOTHER_LIBRARY_IMPORT_ERROR:
    class CustomThing(UsefulThing):
        pass

Another option is to define a substitute base class by modifying the exception handler:

try:
    from another_library import UsefulThing
except ImportError:
    class UsefulThing:
        pass
    ...

Allowed unchecked imports

Ansible allows the following unchecked imports from these specific directories:

ansible-core:
- For lib/ansible/modules/ and lib/ansible/module_utils/, unchecked imports are only allowed from the Python standard library;
- For lib/ansible/plugins/, unchecked imports are only allowed from the Python standard library, from public dependencies of ansible-core, and from ansible-core itself;
collections:
- For plugins/modules/ and plugins/module_utils/, unchecked imports are only allowed from the Python standard library;
- For other directories in plugins/ (see the community collection requirements for a list), unchecked imports are only allowed from the Python standard library, from public dependencies of ansible-core, and from ansible-core itself.

Public dependencies of ansible-core are:

Jinja2

PyYAML

MarkupSafe (as a dependency of Jinja2)

Frequently asked questions (FAQ)

Why do I get an `ImportError` when my module or plugin works?

The import sanity test is very different from other tests. By design, it can only see modules that are in the Python standard library. This means your module or plugin can work in your playbooks, integration tests and unit tests, while failing the import sanity test.