MarkdownSimplechem

Support for chemical equations in Python-Markdown.

Formats chemical equations, written in simple text form, automatically detecting when the number is subscript or not. It also supports superscripts, though with less readable syntax.

Syntax

Chemical equation must be enclosed in {}. For example, {H2O} is a water molecule.

Subscripts:

Detected automatically. In {3H2O}, only '2' is turned to subscript.

Only number-like strings are rendered to subsripts. NUmber-like strings are:

• Strings, composed of numbers 0-9 and decimal point.
• Single question mark

Superscripts

^(text) or ^char

Special characters

Additionally, following special characters are available:

• • middle dot "·"
• -> right arrow "→"
• <-> pair of arrows "⇄"
• <> equilibrium arrow "⇌"
• hnu hν

Installation

Install using pip:

pip install git+https://github.com/dmishin/markdown-simplechem.git

Configuration

The extension has 2 configuration options:

• 'class'::str - CSS class to use for the span element enclosing the formula. Default is 'simplechem'.
• 'prefix'::str - prefix to use for chemical equations. Default is '', that is no prefix.

By default, there is no prefix, and any text enclosed in {} is considered to be a chemical equation. This could cause conflicts with other extensions and template engines, which also use {} for their own purposes. To avoid this, it is possible to configure a prefix, which will be used to detect chemical equations.

For example, to use 'chem' prefix, before creating Markdown object, do this:

md = markdown.Markdown(extensions=['mdx_simplechem'],
                       extension_configs={'mdx_simplechem': {'prefix': 'chem', 
                                                             'class': 'chem'}})

Then, chemical equations will be detected like this: chem{H2O}.

Examples

>>> import markdown
>>> md = markdown.Markdown(extensions=['mdx_simplechem'])
>>> md.convert('This is sugar: {C6H12O6}')
'<p>This is sugar: <span class="simplechem">C<sub>6</sub>H<sub>12</sub>O<sub>6</sub></span></p>'

>>> md.convert('Smart subscript and special chars: {2KOH + H2SO4 -> K2SO4 + H2O}')
'<p>Smart subscript and special chars: <span class="simplechem">2KOH + H<sub>2</sub>SO<sub>4</sub> → K<sub>2</sub>SO<sub>4</sub> + H<sub>2</sub>O</span></p>'

>>> md.convert('Superscript: {2K^+ + O^(2-)}')
'<p>Superscript: <span class="simplechem">2K<sup>+</sup> + O<sup>2-</sup></span></p>'

>>> md.convert('All special chars: {* -> <-> <> hnu}')
'<p>All special chars: <span class="simplechem">· → ⇄ ⇌ hν</span></p>'

>>> md.convert('Fractions: {1/2H2 + 0.5Cl2}')
'<p>Fractions: <span class="simplechem">1/2H<sub>2</sub> + 0.5Cl<sub>2</sub></span></p>'