symmetric 1.2.2

A simple wrapper over Flask to speed up basic API deployments.

Symmetric

A simple wrapper over Flask to speed up basic API deployments.

Why Symmetric?

Raw developing speed and ease of use, that's why. While Flask is a powerful tool to have, getting it to work from scratch can be a bit of a pain, especially if you have never used it before. The idea behind symmetric is to be able to take any module already written and transform it into a working API in a matter of minutes, instead of having to design the module ground-up to work with Flask (it can also be used to build an API from scratch really fast). With symmetric, you will also get some neat features, namely:

• Auto logging.
• Server-side error detection and exception handling.
• Auto-generated documentation for your API.

Installing

Install using pip!

pip install symmetric

Usage

Running the development server

To start the development server, just run:

symmetric run <module>

Where <module> is your module name (in the examples, we will be writing in a file named module.py, so the module name will be just module). A Flask instance will be spawned immediately and can be reached at http://127.0.0.1:5000 by default. We don't have any endpoints yet, so we'll add some later. Do not use this in production. The Flask server is meant for development only. Instead, you can use any WSGI server to run the API. For example, to run the API using gunicorn, you just need to run gunicorn module:symmetric and a production ready server will be spawned.

Defining the API endpoints

The module consists of a main object called symmetric, which includes an important element: the router decorator. Let's analyze it:

from symmetric import symmetric

@symmetric.router("/some-route", methods=["get"], response_code=200)

The decorator recieves 3 arguments: the route argument (the endpoint of the API to which the decorated function will map), the methods argument (a list of the methods accepted to connect to that endpoint, defaults in only GET requests) and the response_code argument (the response code of the endpoint if everything goes according to the plan. Defaults to 200).

Now let's imagine that we have the following method:

def some_function():
    """Greets the world."""
    return "Hello World!"

To transform that method into an API endpoint, all you need to do is add one line:

@symmetric.router("/sample")
def some_function():
    """Greets the world."""
    return "Hello World!"

Run symmetric run module and send a GET request to http://127.0.0.1:5000/sample. You should get a Hello World! in response! (To try it with a browser, make sure to run the above command and click this link).

But what about methods with arguments? Of course they can be API'd too! Let's now say that you have the following function:

def another_function(a, b=372):
    """
    Adds :a and :b and returns the result of
    that operation.
    """
    return a + b

To transform that method into an API endpoint, all you need to do, again, is add one line:

@symmetric.router("/add")
def another_function(a, b=372):
    """
    Adds :a and :b and returns the result of
    that operation.
    """
    return a + b

Auto-generating the API documentation

Generating API documentation is simple with symmetric. Just run the following command:

symmetric docs <module>

This will automagically generate a markdown file documenting each endpoint with the function docstring, required arguments and HTTP methods. Seems too simple to be true, right? Go ahead, try it yourself!

You can also specify the name of the documentation file (defaults to documentation.md) using the -f or the --filename flag.

Querying API endpoints

To give parameters to a function, all we need to do is send a json body with the names of the parameters as keys. Let's see how! Run symmetric run module and send a GET request to http://127.0.0.1:5000/add, now using the requests module.

import requests

payload = {
    "a": 48,
    "b": 21
}
response = requests.get("http://127.0.0.1:5000/add", json=payload)
print(response.json())

We got a 69 response! (48 + 21 = 69). Of course, you can return dictionaries from your methods and those will get returned as a json body in the response object automagically!

With this in mind, you can transform any existing project into a usable API very quickly!

The whole example

To sum up, if the original module.py file looked like this before symmetric:

def some_function():
    """Greets the world."""
    return "Hello World!"


def another_function(a, b=372):
    """
    Adds :a and :b and returns the result of
    that operation.
    """
    return a + b

The complete final module.py file with symmetric should look like this:

from symmetric import symmetric


@symmetric.router("/sample")
def some_function():
    """Greets the world."""
    return "Hello World!"


@symmetric.router("/add")
def another_function(a, b=372):
    """
    Adds :a and :b and returns the result of
    that operation.
    """
    return a + b

To run the server, just run symmetric run module. Now, you can send GET requests to http://127.0.0.1:5000/sample and http://127.0.0.1:5000/add. Here is a simple file to get you started querying your API:

import requests


def call_sample():
    response = requests.get("http://127.0.0.1:5000/sample")
    return response.text


def call_add():
    payload = {
        "a": 48,
        "b": 21
    }
    response = requests.get("http://127.0.0.1:5000/add", json=payload)
    return response.json()


if __name__ == '__main__':
    print(call_sample())
    print(call_add())

Running symmetric docs module would result in a file documentation.md being created with the following content:

# Module API Documentation

## `/add`

### Description

`HTTP` methods accepted: `GET`

Adds :a and :b and returns the result of
that operation.

### Parameters

```py
{
    a,
    b,  # defaults to 372
}
```

## `/sample`

### Description

`HTTP` methods accepted: `GET`

Greets the world.

### Parameters

No required parameters.

Developing

Clone the repository:

git clone https://github.com/daleal/symmetric.git

cd symmetric

Recreate environment:

./environment.sh

. .venv/bin/activate

Build the project:

poetry build

Test install:

poetry install  # will also install the symmetric CLI

Push to TestPyPi:

poetry config repositories.testpypi https://test.pypi.org/legacy/
poetry publish -r testpypi

Download from TestPyPi:

deactivate
rm -rf .testing-venv
python3 -m venv .testing-venv
. .testing-venv/bin/activate
pip install click
python -m pip install --index-url https://test.pypi.org/simple/ symmetric

Push to PyPi:

poetry publish