htexpr 0.1.2

htexpr compiles an html string into a Python expression

htexpr: Templating for Dash

htexpr compiles an html-like template syntax into Python expressions, allowing embedded Python expressions in attributes and content. It is inspired by JSX and intended to complement the excellent Dash package, which allows you to write single-page React apps in Python. For motivation and further instructions, see the documentation.

Example

A Unicode table:

import dash
from dash import dcc, html, Input, Output, State

from htexpr import compile
import unicodedata

app = dash.Dash()
app.layout = compile("""
<div>
  <table style={"margin": "0 auto"}>
    <tr><th>char</th><th>name</th><th>category</th></tr>
       [
         (<tr style={'background-color': '#eee' if line % 2 else '#ccc'}>
            <td>{ char }</td>
            <td>{ unicodedata.name(char, '???') }</td>
            <td>{ unicodedata.category(char) }</td>
          </tr>)
         for line, char in enumerate(chr(i) for i in range(32, 128))
       ]
  </table>
</div>
""").run()

app.run_server(debug=True)

Further demonstrations:

• a larger Unicode table
• a Bootstrap example

Development status

I wrote this to help me with a particular project where I kept making bracketing mistakes. The code works for that project, but there are likely to be corner cases I haven't considered.

The Python grammar used here is quite simplistic: it recognizes strings and variously parenthesized expressions. By understanding more Python it would probably be possible to disambiguate between comparison operators and tags, and thus drop the requirement to enclose nested expressions in parentheses.

The error messages are not always helpful, and in particular the code objects don't yet have reliable line-number data.