live-cells-py 0.2.0

A reactive programming library for Python ported from Live Cells for Dart

Live Cells Python

This software is still in beta, and will likely experience rapid changes before the first official release.

Live Cells Python is a reactive programming library for Python, ported from Live Cells for Dart.

Installation

Run the following command to install Live Cells Python:

pip install live-cells-py

Examples

This section contains examples demonstrating the main features of the library. Head to the documentation, for more information on how to use this library.

The basic building block of Live Cells is the cell, which is an object with a value and a set of observers, which react to changes in the value.

Cells are defined as follows:

import live_cells as lc

a = lc.mutable(0)
a = lc.mutable(0)

And are observed as follows:

lc.watch(lambda: print(f'{a()}, {b()}'))

The watch function defined above prints the values of the cells a and b to standard output. It is called whenever the value of a or b changes.

For example the following code, which sets the values of a and b:

a.value = 1
b.value = 2
a.value = 3

Results in the following being printed to standard output:

1, 0
1, 2
3, 2

Watch functions comprising multiple statements can be defined using the decorator of watch:

@lc.watch
def watcher():
    print(f'A = {a()}')
    print(f'B = {b()}')

Cells can also be defined as a function of the values of one or more cells. For example the following cell is defined as the sum of cells a and b:

c = lc.computed(lambda: a() + b())

The value of cell c is recomputed automatically whenever the value of either a or b changes.

This cell can also be defined more succinctly as an expression of cells:

c = a + b

That looks exactly like a normal variable definition.

This can be used to run a routine automatically whenever a certain condition is met. For example, let's print a message to standard output whenever the sum exceeds 100:

@lc.watch
def watch_sum():
    if c() > 100:
        print('Sum exceeds 100!!!')

When the following is executed:

a.value = 90
b.value = 30

The following message is printed to standard output automatically:

Sum exceeds 100!!!