Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

https://github.com/garethr/pycnab

Python library for manipulating Cloud Native Application Bundles
https://github.com/garethr/pycnab

cnab python python3

Last synced: 3 months ago
JSON representation

Python library for manipulating Cloud Native Application Bundles

Lists

README 

        
# Python CNAB Library



_Work-in-progress_ library for working with [CNAB](https://cnab.io/) in Python.



There are probably three main areas of interest for a CNAB client:



1. Handling the `bundle.json` format ([101](https://github.com/deislabs/cnab-spec/blob/master/101-bundle-json.md))

2. Building invocation images ([102](https://github.com/deislabs/cnab-spec/blob/master/102-invocation-image.md))

3. Running actions against a CNAB ([103](https://github.com/deislabs/cnab-spec/blob/master/103-bundle-runtime.md))



Claims and Signing are optional but will be worked on once the above are stable.



## Installation



The module is published on [PyPi](https://pypi.org/project/cnab/) and can be installed from there.



```bash

pip install cnab

```



## Parsing `bundle.json`



Nothing too fancy here, the `Bundle` class  has a `from_dict` static method which

builds a full `Bundle` object.



```python

import json

from cnab import Bundle



with open("bundle.json") as f:

    data = json.load(f)



bundle = Bundle.from_dict(data)

```



This could for example be used for validation purposes, or for building user interfaces for `bundle.json` files.



## Describing `bundle.json` in Python 



You can also describe the `bundle.json` file in Python. This will correctly validate the

structure based on the current specification and would allow for building a custom DSL or other

user interface for generating `bundle.json` files.



```python

from cnab import Bundle, InvocationImage



bundle = Bundle(

    name="hello",

    version="0.1.0",

    invocation_images=[

        InvocationImage(

            image_type="docker",

            image="technosophos/helloworld:0.1.0",

            digest="sha256:aaaaaaa...",

        )

    ],

)



print(bundle.to_json())

```



## Running CNABs



The module supports running actions on a CNAB, using the `docker` driver.



```python

from cnab import CNAB



# The first argument can be a path to a bundle.json file, a dictionary

# or a full `Bundle` object

app = CNAB("fixtures/helloworld/bundle.json")



# list available actions

print(app.actions)



# list available parameters

print(app.parameter)



# run the install action

print(app.run("install"))



# run the install action specifying a parameters

print(app.run("install", parameters={"port": 9090}))



# Many applications will require credentials

app = CNAB("fixtures/hellohelm/bundle.json")



# list required credentials

print(app.credentials)



# Here we pass the value for the required credential

# in this case by reading the existing configuration from disk

with open("/home/garethr/.kube/config") as f:

    print(app.run("status", credentials={"kubeconfig": f.read()}))

```



Note that error handling for this is very work-in-progress.



## Working with invocation images



`pycnab` also has a class for working with invocation images.



```python

from cnab import CNABDirectory



directory = CNABDirectory("fixtures/invocationimage")



# Check whether the directory is valid

# Raises `InvalidCNABDirectory` exception if invalid

directory.valid()



# Returns the text of the associated README file if present

directory.readme()



# Returns the text of the associated LICENSE file if present

directory.license()

```



## Thanks



Thanks to [QuickType](https://quicktype.io/) for bootstrapping the creation of the Python code for manipulating `bundle.json` based on the current JSON Schema.