Reflex

🕸️ Web apps in pure Python 🐍

Description

Reflex is a library to build full-stack web apps in pure Python.

Key features:

Programming language: Python

License: Apache License 2.0

Tags: GUI     Visualization     User Interfaces     Widget Sets    

README

The easiest way to build and deploy web apps.

Getting Started

Pynecone is a full-stack python framework that makes it easy to build and deploy web apps in minutes.

All the information for getting started can be found in this README, however, a more detailed explanation of the following topics can be found on our website:

Introduction | Component Library | Examples | Deployment

Installation

Pynecone requires to following to get started:

• Python 3.7+
• NodeJS 12.22.0+

$ pip install pynecone-io

Create your first Pynecone app

Installing Pynecone also installs the pc command line tool. Test that the install was successful by creating a new project.

Replace my_app_name with your project name:

$ mkdir my_app_name
$ cd my_app_name
$ pc init

This initializes a template app in your new directory. You can run this app in development mode:

$ pc run

You should see your app running at http://localhost:3000.

Note that the port may be different if you have another app running on port 3000.

Now you can modify the source code in my_app_name/my_app_name.py. Pynecone has fast refreshes so you can see your changes instantly when you save your code.

Example App

Let's go over a simple counter app to explore the basics of Pynecone.

Here is the complete code to create this.

import pynecone as pc
import random

class State(pc.State):
    count = 0

    def increment(self):
        """Increment the count."""
        self.count += 1

    def decrement(self):
        """Decrement the count."""
        self.count -= 1

    def random(self):
        """Randomize the count."""
        self.count = random.randint(0, 100)


def index():
    """The main view."""
    return pc.center(
        pc.vstack(
            pc.heading(State.count),
            pc.hstack(
                pc.button("Decrement", on_click=State.decrement, color_scheme="red"),
                pc.button(
                    "Randomize",
                    on_click=State.random,
                    background_image="linear-gradient(90deg, rgba(255,0,0,1) 0%, rgba(0,176,34,1) 100%)",
                    color="white",
                ),
                pc.button("Increment", on_click=State.increment, color_scheme="green"),
            ),
            padding="1em",
            bg="#ededed",
            border_radius="1em",
            box_shadow="lg",
        ),
        padding_y="5em",
        font_size="2em",
        text_align="center",
    )


# Add state and page to the app.
app = pc.App(state=State)
app.add_page(index, title="Counter")
app.compile()

Let's break this down.

• ### State

class State(pc.State):
    count = 0 

The state defines all the variables (called vars) in an app that can change, as well as the functions that change them. Here our state has by a single var, count, which holds the current value of the counter. The frontend of the app is a reflection of the current state.

• ### Event Handlers ```python def increment(self): """Increment the count.""" self.count += 1

def decrement(self): """Decrement the count.""" self.count -= 1

def random(self): """Randomize the count.""" self.count = random.randint(0, 100)

Within the state, we define functions, called event handlers, that change the state vars.
Event handlers are the only way that we can modify the state in Pynecone. They can be called in response to user actions, such as clicking a button or typing in a text box. These actions are called events.
Our counter app has two event handlers, increment and decrement.

* ### Frontend

```python 
def index():
    return pc.center(
        pc.vstack(
            pc.heading(State.count),
            pc.hstack(
                pc.button("Decrement", on_click=State.decrement, color_scheme="red"),
                pc.button(
                    "Randomize",
                    on_click=State.random,
                    background_image="linear-gradient(90deg, rgba(255,0,0,1) 0%, rgba(0,176,34,1) 100%)",
                    color="white",
                ),
                pc.button("Increment", on_click=State.increment, color_scheme="green"),
            ),
            padding="1em",
            bg="#ededed",
            border_radius="1em",
            box_shadow="lg",
        ),
        padding_y="5em",
        font_size="2em",
        text_align="center",
    )

This function defines the frontend of the app. We use different components such as pc.box, pc.button, and pc.heading to build the frontend. Components can be nested to create complex layouts, and can be styled using the full power of CSS.

Pynecone comes with 50+ built-in components to help you get started. We are actively adding more components, plus it's easy to create your own components.

• ### Routing

Next we define our app and tell it what state to use.

app = pc.App(state=State)

We add a route from the root of the app to the counter component. By default the route

app.add_page(index)

You can create a multi-page app by adding more routes.

Contributing

Pull requests are encouraged and always welcome. Pick an issue and help us out, or submit an issue id something is not working or confusing!

More Information

More information about Pynecone can be found on our website, https://pynecone.io

License

Pynecone is open-source and licensed under the [Apache License 2.0](LICENSE)