Reference
Python package for creating custom GitHub Actions.
The file is mandatory for build system to find the package.
Classes
Base class for GitHub Actions.
You should implement main() method in the subclass.
You can define custom inputs and / or outputs types in the subclass. You can do nothing in the subclass if you don't need typed inputs and outputs.
Note these are just types, instances of these types are automatically created in the __init__ method.
Usage:
class MyInputs(ActionInputs):
my_input: str
'''My input description'''
my_path: Path
'''My path description'''
class MyOutputs(ActionOutputs):
runner_os: str
'''Runner OS description'''
class MyAction(ActionBase):
inputs: MyInputs
outputs: MyOutputs
def main(self):
if self.inputs.my_path is None:
raise ValueError("my-path is required")
self.inputs.my_path.mkdir(exist_ok=True)
self.outputs.runner_os = self.env.runner_os
self.summary.text += (
self.render(
"### {{ inputs.my_input }}.\n"
"Have a nice day, {{ inputs['name'] }}!"
)
)
if __name__ == "__main__":
MyAction().run()
Attributes
instance-attribute
environment = Environment(loader=FileSystemLoader(str(templates_dir)))
instance-attribute
outputs: ActionOutputs = types['outputs']()
class-attribute
instance-attribute
summary = FileTextProperty('github_step_summary')
Functions
main() -> None
Business logic of the action.
Is called by run() method.
render(template: str, **kwargs: Any) -> str
Render the template from the string with Jinja.
kwargs are the template context variables.
Also includes to the context the action's inputs, outputs, and env.
So you can use something like:
self.render("### {{ inputs.name }}!\nHave a nice day!")
render_template(template_name: str, **kwargs: Any) -> str
Render template from the templates directory.
template_name is the name of the template file without the extension.
kwargs are the template context variables.
Also includes to the context the action's inputs, outputs, and env.
Usage:
self.render_template("executor.json", image="ubuntu-latest")
run() -> None
Run the action.
run() calls the main() method of the action with the necessary boilerplate to catch and
report exceptions.
Usage:
if __name__ == "__main__":
MyAction().run()
main() is where you implement the business logic of your action.
Bases: EnvAttrDictVars
GitHub Action input variables.
Usage:
class MyInputs(ActionInputs):
my_input: str
action = ActionBase(inputs=MyInputs())
print(action.inputs.my_input)
print(action.inputs["my-input"]) # the same as above
With attributes, you can only access explicitly declared vars, with dict-like access you can access any var. This way you can find your balance between strictly defined vars and flexibility.
Attribute names are converted to kebab-case.
So action.inputs.my_input is the same as action.inputs["my-input"].
If you need to access a snake_case named input my_input, you should
use dict-style only: action.inputs["my_input"].
But it's common to use kebab-case in GitHub Actions input names.
By GitHub convention, all input names are upper-cased in the environment and prefixed with "INPUT_".
So actions.inputs.my_input or actions.inputs['my-input'] will be the variable INPUT_MY-INPUT
in the environment.
The ActionInputs does the conversion automatically.
Uses lazy loading of the values. So the value is read from the environment only when accessed and only once, and saved in the object's internal dict.
Bases: FileAttrDictVars
GitHub Actions output variables.
Usage:
class MyOutputs(ActionOutputs):
my_output: str
action = ActionBase(outputs=MyOutputs())
action.outputs["my-output"] = "value"
action.outputs.my_output = "value" # the same as above
With attributes, you can only access explicitly declared vars, with dict-like access you can access any var. This way you can find your balance between strictly defined vars and flexibility.
Attribute names are converted to kebab-case.
So action.outputs.my_output is the same as action.outputs["my-output"].
If you need to access a snake_case named output like my_output you should
use dict-style only: action.outputs["my_output"].
But it's common to use kebab-case in GitHub Actions output names.
Each output var assignment changes the GitHub outputs file
(the path is defined as action.env.github_output).
Bases: EnvAttrDictVars
GitHub Action environment variables.
https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables
Usage:
class MyAction:
@property
def env(self):
return GithubVars()
action = MyAction()
print(action.env.github_repository)
Thanks to the docstrings your IDE will provide you with doc hints when you hover over the property. We do not load the attributes on the class init but do it Lazily. Once read, the value is stored in the instance dictionary and is not extracted from env anymore.
Converts attribute names to uppercase. Leave dict-style names unchanged.
Paths and files have type Path.
Attributes
instance-attribute
CI: str
Always set to true.
instance-attribute
github_action: str
The name of the action currently running, or the id of a step. For example, for an action, __repo-owner_name-of-action-repo. GitHub removes special characters, and uses the name __run when the current step runs a script without an id. If you use the same script or action more than once in the same job, the name will include a suffix that consists of the sequence number preceded by an underscore. For example, the first script you run will have the name __run, and the second script will be named __run_2. Similarly, the second invocation of actions/checkout will be actionscheckout2.
instance-attribute
github_action_path: Path
The path where an action is located. This property is only supported in composite actions. You can use this path to change directories to where the action is located and access other files in that same repository. For example, /home/runner/work/_actions/repo-owner/name-of-action-repo/v1.
instance-attribute
github_action_repository: str
For a step executing an action, this is the owner and repository name of the action. For example, actions/checkout.
instance-attribute
github_actions: str
Always set to true when GitHub Actions is running the workflow. You can use this variable to differentiate when tests are being run locally or by GitHub Actions.
instance-attribute
github_actor: str
The name of the person or app that initiated the workflow. For example, octocat.
instance-attribute
github_actor_id: str
The account ID of the person or app that triggered the initial workflow run. For example, 1234567. Note that this is different from the actor username.
instance-attribute
github_api_url: str
Returns the API URL. For example: https://api.github.com.
instance-attribute
github_base_ref: str
The name of the base ref or target branch of the pull request in a workflow run. This is only set when the event that triggers a workflow run is either pull_request or pull_request_target. For example, main.
instance-attribute
github_env: str
The path on the runner to the file that sets variables from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/set_env_87406d6e-4979-4d42-98e1-3dab1f48b13a. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_event_name: str
The name of the event that triggered the workflow. For example, workflow_dispatch.
instance-attribute
github_event_path: Path
The path to the file on the runner that contains the full event webhook payload. For example, /github/workflow/event.json.
instance-attribute
github_graphql_url: str
Returns the GraphQL API URL. For example: https://api.github.com/graphql.
instance-attribute
github_head_ref: str
The head ref or source branch of the pull request in a workflow run. This property is only set when the event that triggers a workflow run is either pull_request or pull_request_target. For example, feature-branch-1.
instance-attribute
github_job: str
The job_id of the current job. For example, greeting_job.
instance-attribute
github_output: Path
The path on the runner to the file that sets the current step's outputs from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/set_output_a50ef383-b063-46d9-9157-57953fc9f3f0. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_path: Path
The path on the runner to the file that sets system PATH variables from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/add_path_899b9445-ad4a-400c-aa89-249f18632cf5. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_ref: str
The fully-formed ref of the branch or tag that triggered the workflow run. For workflows
triggered by push, this is the branch or tag ref that was pushed. For workflows triggered by
pull_request, this is the pull request merge branch. For workflows triggered by release,
this is the release tag created. For other triggers, this is the branch or tag ref that
triggered the workflow run. This is only set if a branch or tag is available for the
event type. The ref given is fully-formed, meaning that for branches the format is
refs/heads/
instance-attribute
github_ref_name: str
The short ref name of the branch or tag that triggered the workflow run. This value matches
the branch or tag name shown on GitHub. For example, feature-branch-1.
For pull requests, the format is
instance-attribute
github_ref_protected: str
true if branch protections or rulesets are configured for the ref that triggered the workflow run.
instance-attribute
github_ref_type: str
The type of ref that triggered the workflow run. Valid values are branch or tag.
instance-attribute
github_repository: str
The owner and repository name. For example, octocat/Hello-World.
instance-attribute
github_repository_id: str
The ID of the repository. For example, 123456789. Note that this is different from the repository name.
instance-attribute
github_repository_owner: str
The repository owner's name. For example, octocat.
instance-attribute
github_repository_owner_id: str
The repository owner's account ID. For example, 1234567. Note that this is different from the owner's name.
instance-attribute
github_retention_days: str
The number of days that workflow run logs and artifacts are kept. For example, 90.
instance-attribute
github_run_attempt: str
A unique number for each attempt of a particular workflow run in a repository. This number begins at 1 for the workflow run's first attempt, and increments with each re-run. For example, 3.
instance-attribute
github_run_id: str
A unique number for each workflow run within a repository. This number does not change if you re-run the workflow run. For example, 1658821493.
instance-attribute
github_run_number: str
A unique number for each run of a particular workflow in a repository. This number begins at 1 for the workflow's first run, and increments with each new run. This number does not change if you re-run the workflow run. For example, 3.
instance-attribute
github_server_url: str
The URL of the GitHub server. For example: https://github.com.
instance-attribute
github_sha: str
The commit SHA that triggered the workflow. The value of this commit SHA depends on the event that triggered the workflow. For more information, see "Events that trigger workflows." For example, ffac537e6cbbf934b08745a378932722df287a53.
instance-attribute
github_step_summary: Path
The path on the runner to the file that contains job summaries from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/_layout/_work/_temp/_runner_file_commands/step_summary_1cb22d7f-5663-41a8- 9ffc-13472605c76c. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_triggering_actor: str
The username of the user that initiated the workflow run. If the workflow run is a re-run, this value may differ from github.actor. Any workflow re-runs will use the privileges of github.actor, even if the actor initiating the re-run (github.triggering_actor) has different privileges.
instance-attribute
github_workflow: str
The name of the workflow. For example, My test workflow. If the workflow file doesn't specify a name, the value of this variable is the full path of the workflow file in the repository.
instance-attribute
github_workflow_ref: str
The ref path to the workflow. For example, octocat/hello-world/.github/workflows/my-workflow.yml@ refs/heads/my_branch.
instance-attribute
github_workflow_sha: str
The commit SHA for the workflow file.
instance-attribute
github_workspace: Path
The default working directory on the runner for steps, and the default location of your repository when using the checkout action. For example, /home/runner/work/my-repo-name/my-repo-name.
instance-attribute
runner_arch: str
The architecture of the runner executing the job. Possible values are X86, X64, ARM, or ARM64.
instance-attribute
runner_debug: str
This is set only if debug logging is enabled, and always has the value of 1. It can be useful as an indicator to enable additional debugging or verbose logging in your own job steps.
instance-attribute
runner_name: str
The name of the runner executing the job. This name may not be unique in a workflow run as runners at the repository and organization levels could use the same name. For example, Hosted Agent
instance-attribute
runner_os: str
The operating system of the runner executing the job. Possible values are Linux, Windows, or macOS. For example, Windows
instance-attribute
runner_temp: Path
The path to a temporary directory on the runner. This directory is emptied at the beginning and end of each job. Note that files will not be removed if the runner's user account does not have permission to delete them. For example, D:\a_temp
instance-attribute
runner_tool_cache: str
The path to the directory containing preinstalled tools for GitHub-hosted runners. For more information, see "Using GitHub-hosted runners". For example, C:\hostedtoolcache\windows
Modules
Classes
Base class for GitHub Actions.
You should implement main() method in the subclass.
You can define custom inputs and / or outputs types in the subclass. You can do nothing in the subclass if you don't need typed inputs and outputs.
Note these are just types, instances of these types are automatically created in the __init__ method.
Usage:
class MyInputs(ActionInputs):
my_input: str
'''My input description'''
my_path: Path
'''My path description'''
class MyOutputs(ActionOutputs):
runner_os: str
'''Runner OS description'''
class MyAction(ActionBase):
inputs: MyInputs
outputs: MyOutputs
def main(self):
if self.inputs.my_path is None:
raise ValueError("my-path is required")
self.inputs.my_path.mkdir(exist_ok=True)
self.outputs.runner_os = self.env.runner_os
self.summary.text += (
self.render(
"### {{ inputs.my_input }}.\n"
"Have a nice day, {{ inputs['name'] }}!"
)
)
if __name__ == "__main__":
MyAction().run()
instance-attribute
environment = Environment(loader=FileSystemLoader(str(templates_dir)))
instance-attribute
inputs: ActionInputs = types['inputs']()
instance-attribute
outputs: ActionOutputs = types['outputs']()
class-attribute
instance-attribute
summary = FileTextProperty('github_step_summary')
main() -> None
Business logic of the action.
Is called by run() method.
render(template: str, **kwargs: Any) -> str
Render the template from the string with Jinja.
kwargs are the template context variables.
Also includes to the context the action's inputs, outputs, and env.
So you can use something like:
self.render("### {{ inputs.name }}!\nHave a nice day!")
render_template(template_name: str, **kwargs: Any) -> str
Render template from the templates directory.
template_name is the name of the template file without the extension.
kwargs are the template context variables.
Also includes to the context the action's inputs, outputs, and env.
Usage:
self.render_template("executor.json", image="ubuntu-latest")
run() -> None
Run the action.
run() calls the main() method of the action with the necessary boilerplate to catch and
report exceptions.
Usage:
if __name__ == "__main__":
MyAction().run()
main() is where you implement the business logic of your action.
Property descriptor read / write from a file.
Classes
Common base class for accessing variables as attributes or dict.
Classes
Bases: AttrDictVars
Dual access env vars.
Access to env vars as object attributes or as dict items. Do not allow changing vars, so this is a read-only source of env vars values.
With attributes, you can only access explicitly declared vars, with dict-like access you can access any var. This way you can find your balance between strictly defined vars and flexibility.
Usage:
class MyVars(EnvAttrDictVars):
documented_var: str
vars = MyVars(prefix="INPUT_")
print(vars["undocumented_var"]) # from os.environ["INPUT_UNDOCUMENTED_VAR"]
print(vars.documented_var) # from os.environ["INPUT_DOCUMENTED-VAR"]
Attribute names are converted with the method _attr_to_var_name() - it converts Python attribute
names from snake_case to kebab-case.
Classes
Bases: AttrDictVars, MutableMapping
Dual access vars in a file.
File contains vars as key=value lines.
Access with attributes or as dict.
With attributes, you can only access explicitly declared vars, with dict-like access you can access any var. This way you can find your balance between strictly defined vars and flexibility.
Usage: class MyVars(FileAttrDictVars): documented_var: str
vars = MyVars(Path("my_vars.txt")) vars["undocumented_var"] = "value1" vars.documented_var == "value2"
# Produces "my_vars.txt" with: # documented-var=value2 # undocumented_var=value1
On read/write, it converts var names with _name_from_external()/_external_name() methods.
They remove/add _external_name_prefix to the names.
Attribute access also uses _attr_to_var_name() - by default it converts Python attribute names
from snake_case to kebab-case.
Classes
Bases: EnvAttrDictVars
GitHub Action environment variables.
https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables
Usage:
class MyAction:
@property
def env(self):
return GithubVars()
action = MyAction()
print(action.env.github_repository)
Thanks to the docstrings your IDE will provide you with doc hints when you hover over the property. We do not load the attributes on the class init but do it Lazily. Once read, the value is stored in the instance dictionary and is not extracted from env anymore.
Converts attribute names to uppercase. Leave dict-style names unchanged.
Paths and files have type Path.
instance-attribute
CI: str
Always set to true.
instance-attribute
github_action: str
The name of the action currently running, or the id of a step. For example, for an action, __repo-owner_name-of-action-repo. GitHub removes special characters, and uses the name __run when the current step runs a script without an id. If you use the same script or action more than once in the same job, the name will include a suffix that consists of the sequence number preceded by an underscore. For example, the first script you run will have the name __run, and the second script will be named __run_2. Similarly, the second invocation of actions/checkout will be actionscheckout2.
instance-attribute
github_action_path: Path
The path where an action is located. This property is only supported in composite actions. You can use this path to change directories to where the action is located and access other files in that same repository. For example, /home/runner/work/_actions/repo-owner/name-of-action-repo/v1.
instance-attribute
github_action_repository: str
For a step executing an action, this is the owner and repository name of the action. For example, actions/checkout.
instance-attribute
github_actions: str
Always set to true when GitHub Actions is running the workflow. You can use this variable to differentiate when tests are being run locally or by GitHub Actions.
instance-attribute
github_actor: str
The name of the person or app that initiated the workflow. For example, octocat.
instance-attribute
github_actor_id: str
The account ID of the person or app that triggered the initial workflow run. For example, 1234567. Note that this is different from the actor username.
instance-attribute
github_api_url: str
Returns the API URL. For example: https://api.github.com.
instance-attribute
github_base_ref: str
The name of the base ref or target branch of the pull request in a workflow run. This is only set when the event that triggers a workflow run is either pull_request or pull_request_target. For example, main.
instance-attribute
github_env: str
The path on the runner to the file that sets variables from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/set_env_87406d6e-4979-4d42-98e1-3dab1f48b13a. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_event_name: str
The name of the event that triggered the workflow. For example, workflow_dispatch.
instance-attribute
github_event_path: Path
The path to the file on the runner that contains the full event webhook payload. For example, /github/workflow/event.json.
instance-attribute
github_graphql_url: str
Returns the GraphQL API URL. For example: https://api.github.com/graphql.
instance-attribute
github_head_ref: str
The head ref or source branch of the pull request in a workflow run. This property is only set when the event that triggers a workflow run is either pull_request or pull_request_target. For example, feature-branch-1.
instance-attribute
github_job: str
The job_id of the current job. For example, greeting_job.
instance-attribute
github_output: Path
The path on the runner to the file that sets the current step's outputs from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/set_output_a50ef383-b063-46d9-9157-57953fc9f3f0. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_path: Path
The path on the runner to the file that sets system PATH variables from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/add_path_899b9445-ad4a-400c-aa89-249f18632cf5. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_ref: str
The fully-formed ref of the branch or tag that triggered the workflow run. For workflows
triggered by push, this is the branch or tag ref that was pushed. For workflows triggered by
pull_request, this is the pull request merge branch. For workflows triggered by release,
this is the release tag created. For other triggers, this is the branch or tag ref that
triggered the workflow run. This is only set if a branch or tag is available for the
event type. The ref given is fully-formed, meaning that for branches the format is
refs/heads/
instance-attribute
github_ref_name: str
The short ref name of the branch or tag that triggered the workflow run. This value matches
the branch or tag name shown on GitHub. For example, feature-branch-1.
For pull requests, the format is
instance-attribute
github_ref_protected: str
true if branch protections or rulesets are configured for the ref that triggered the workflow run.
instance-attribute
github_ref_type: str
The type of ref that triggered the workflow run. Valid values are branch or tag.
instance-attribute
github_repository: str
The owner and repository name. For example, octocat/Hello-World.
instance-attribute
github_repository_id: str
The ID of the repository. For example, 123456789. Note that this is different from the repository name.
instance-attribute
github_repository_owner: str
The repository owner's name. For example, octocat.
instance-attribute
github_repository_owner_id: str
The repository owner's account ID. For example, 1234567. Note that this is different from the owner's name.
instance-attribute
github_retention_days: str
The number of days that workflow run logs and artifacts are kept. For example, 90.
instance-attribute
github_run_attempt: str
A unique number for each attempt of a particular workflow run in a repository. This number begins at 1 for the workflow run's first attempt, and increments with each re-run. For example, 3.
instance-attribute
github_run_id: str
A unique number for each workflow run within a repository. This number does not change if you re-run the workflow run. For example, 1658821493.
instance-attribute
github_run_number: str
A unique number for each run of a particular workflow in a repository. This number begins at 1 for the workflow's first run, and increments with each new run. This number does not change if you re-run the workflow run. For example, 3.
instance-attribute
github_server_url: str
The URL of the GitHub server. For example: https://github.com.
instance-attribute
github_sha: str
The commit SHA that triggered the workflow. The value of this commit SHA depends on the event that triggered the workflow. For more information, see "Events that trigger workflows." For example, ffac537e6cbbf934b08745a378932722df287a53.
instance-attribute
github_step_summary: Path
The path on the runner to the file that contains job summaries from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/_layout/_work/_temp/_runner_file_commands/step_summary_1cb22d7f-5663-41a8- 9ffc-13472605c76c. For more information, see "Workflow commands for GitHub Actions".
instance-attribute
github_triggering_actor: str
The username of the user that initiated the workflow run. If the workflow run is a re-run, this value may differ from github.actor. Any workflow re-runs will use the privileges of github.actor, even if the actor initiating the re-run (github.triggering_actor) has different privileges.
instance-attribute
github_workflow: str
The name of the workflow. For example, My test workflow. If the workflow file doesn't specify a name, the value of this variable is the full path of the workflow file in the repository.
instance-attribute
github_workflow_ref: str
The ref path to the workflow. For example, octocat/hello-world/.github/workflows/my-workflow.yml@ refs/heads/my_branch.
instance-attribute
github_workflow_sha: str
The commit SHA for the workflow file.
instance-attribute
github_workspace: Path
The default working directory on the runner for steps, and the default location of your repository when using the checkout action. For example, /home/runner/work/my-repo-name/my-repo-name.
instance-attribute
runner_arch: str
The architecture of the runner executing the job. Possible values are X86, X64, ARM, or ARM64.
instance-attribute
runner_debug: str
This is set only if debug logging is enabled, and always has the value of 1. It can be useful as an indicator to enable additional debugging or verbose logging in your own job steps.
instance-attribute
runner_name: str
The name of the runner executing the job. This name may not be unique in a workflow run as runners at the repository and organization levels could use the same name. For example, Hosted Agent
instance-attribute
runner_os: str
The operating system of the runner executing the job. Possible values are Linux, Windows, or macOS. For example, Windows
instance-attribute
runner_temp: Path
The path to a temporary directory on the runner. This directory is emptied at the beginning and end of each job. Note that files will not be removed if the runner's user account does not have permission to delete them. For example, D:\a_temp
instance-attribute
runner_tool_cache: str
The path to the directory containing preinstalled tools for GitHub-hosted runners. For more information, see "Using GitHub-hosted runners". For example, C:\hostedtoolcache\windows
Github Actions helper functions.
We want to support Python 3.7 that you still have on some self-hosted action runners. So no fancy features like walrus operator, @cached_property, etc.
Attributes
module-attribute
INPUT_PREFIX = 'INPUT_'
Classes
Bases: EnvAttrDictVars
GitHub Action input variables.
Usage:
class MyInputs(ActionInputs):
my_input: str
action = ActionBase(inputs=MyInputs())
print(action.inputs.my_input)
print(action.inputs["my-input"]) # the same as above
With attributes, you can only access explicitly declared vars, with dict-like access you can access any var. This way you can find your balance between strictly defined vars and flexibility.
Attribute names are converted to kebab-case.
So action.inputs.my_input is the same as action.inputs["my-input"].
If you need to access a snake_case named input my_input, you should
use dict-style only: action.inputs["my_input"].
But it's common to use kebab-case in GitHub Actions input names.
By GitHub convention, all input names are upper-cased in the environment and prefixed with "INPUT_".
So actions.inputs.my_input or actions.inputs['my-input'] will be the variable INPUT_MY-INPUT
in the environment.
The ActionInputs does the conversion automatically.
Uses lazy loading of the values. So the value is read from the environment only when accessed and only once, and saved in the object's internal dict.
Bases: FileAttrDictVars
GitHub Actions output variables.
Usage:
class MyOutputs(ActionOutputs):
my_output: str
action = ActionBase(outputs=MyOutputs())
action.outputs["my-output"] = "value"
action.outputs.my_output = "value" # the same as above
With attributes, you can only access explicitly declared vars, with dict-like access you can access any var. This way you can find your balance between strictly defined vars and flexibility.
Attribute names are converted to kebab-case.
So action.outputs.my_output is the same as action.outputs["my-output"].
If you need to access a snake_case named output like my_output you should
use dict-style only: action.outputs["my_output"].
But it's common to use kebab-case in GitHub Actions output names.
Each output var assignment changes the GitHub outputs file
(the path is defined as action.env.github_output).