pypods 0.1.3

A lightweight solution to execute Python dependencies in an isolated fashion.

PyPods

A lightweight solution to execute Python dependencies in an isolated fashion.

This documentation will follow the classic philosophy of A picture is worth a thousand words

Problem

Solution

PyPod 🔎

Terminology

1. pods directory stores all the pods that will be used in the current project.
2. A pod is a container that contains its own Python interpreter, dependencies, and a pod.py file that exposes specific functions defined by the user.
3. A pod client is a file that calls the specific functions defined by the user.
4. A pod protocol is a way to exchange data between the pod and pod client. PyPods uses binary json or bson.

How to use PyPods?

1. Install pypods package via pip install pypods
2. From the project's root directory, create a file (say client.py) and paste the following code.

# client.py will communicate with the hello_world_pod pod
from pypods.pods import PodLoader

# name of the pod, and namespace to inject pod's functions.
pl = PodLoader("hello_world_pod", globals())
pl.load_pod()   # Load pod's namespace
pl.unload_pod() # Unload pod's namespace

if hello_world_pod does not exist then PodLoader will create a hello_world_pod pod in the pods/hello_world_pod/ directory.

3. Navigate to pods/hello_world_pod/ directory and observe the file structure. This is your pod.

hello_world_pod/
│
├── venv/
│   ├── bin/          (or Scripts/ on Windows)
│   ├── include/
│   ├── lib/
│   └── pyvenv.cfg
│
├── pod.py
├── requirements.txt

4. You can define functions inside a placeholder defined in the pod.py template file. Please don't change anything else in this file!

# Template pod.py file inside the hello_world_pod pod.
"""
Write your module's functions in this area.
"""
def foo(x, y):
    return x + y

# Don't change anything here!
if __name__ == "__main__":
    from pypods.pods import PodListener
    pl = PodListener()  # PodListener will send output back to the pod client.
    msg = (
        pl.read_stdin()
    )  # Pod client writes function name and parameters to pod's stdin.
    if msg:
        # Unpack stdin to get function data
        function_name, args, kwargs = msg["name"], msg["args"], msg["kwargs"]
        try:
            # Check if function exists in pod module's namespace.
            # If yes, execute the function and send output back to the pod client.
            # If no, send error back to the pod client.
            if function_name in globals():
                function_output = globals()[function_name](*args, **kwargs)
                pl.write_stdout(function_output)
            else:
                pl.write_stderr(f"Function {function_name} does not exist in pod")
        except Exception as e:
            # Any error that occurs while calling the function is sent back to pod client.
            pl.write_stderr(str(e))

5. Go back to client.py and add the foo function.

# client.py will communicate with the hello_world_pod pod
from pypods.pods import PodLoader

# name of the pod, and namespace to inject pod's functions.
pl = PodLoader("hello_world_pod", globals())
pl.load_pod()   # Load pod's namespace (This will now load the foo function).
foo_output = foo(1, 2) # Expected output = 1 + 2 = 3.
pl.unload_pod() # Unload pod's namespace

This demo shows how PyPod works. You ran a pod function foo without importing it into the client.py file! See example/ directory for a project example.

Author

Rohan Deshpande, PyPods 2024. Inspired by the idea of Babashka pods.