pyrx-nlt

Natural Language Template (NLT) Engine — Plain-English templates that non-technical teams can read, write, and maintain for email, notifications, and dynamic content.

Installation

pip install pyrx-nlt

Requires Python 3.10+. Zero third-party dependencies.

Quick Start

from pyrx_nlt import NLTRenderer

renderer = NLTRenderer(
    contact={"first_name": "Alice", "properties": {"Plan": "premium", "Points": 1250}},
    trigger_event={"event_name": "purchase", "attributes": {"Item": "Widget", "Amount": "49.99"}},
)

result = renderer.render(
    subject_template='Order confirmation for {the user\'s First Name, or "Customer"}',
    body_template="""
        <h1>Thank you, {the user's First Name}!</h1>
        <p>You purchased: {the Item from the trigger event}</p>
        <p>Amount: {the Amount from the trigger event, as "currency"}</p>
        {if the user's Plan is premium}
            <p>You earned {the user's Points, as "currency"} in rewards!</p>
        {else}
            <p>Upgrade to Premium for rewards on every purchase.</p>
        {end if}
    """,
)

print(result.html)      # Rendered HTML
print(result.subject)   # "Order confirmation for Alice"
print(result.suppressed) # False

Features

• 3 data sources: {the user's X}, {the X from the trigger event}, {the X from the Y event}
• Modifiers: or "fallback", required, as "format", uppercase/lowercase/titlecase
• Math: plus, minus, times, divided by, modulo
• Conditionals: {if}...{else if}...{else}...{end if} with 20 comparison operators, AND/OR/NOT
• Loops: {for item in source}...{end for} with loop.index, loop.first, loop.last
• Lists: {list source, as comma/ordered/unordered list}
• Tables: {table source with columns: A, B, C}
• Aggregates: {sum of}, {average of}, {count of}
• 19 chainable filters: truncate, replace, url_encode, round, default, strip_html, trim, newline_to_br, split, join, first, last, length, sort, reverse, unique, where, map, slice
• Formatting: 17 currency codes, date presets, custom date tokens, percentages
• Variable assignment: {set x to expression}
• Ternary: {condition ? "true" : "false"}
• Comments: {# ignored #}
• Raw blocks: {raw}...{end raw}
• Macros: {define name(params)}...{end define} / {use name(args)}
• Template inheritance: {extends "base.html"} / {block name}...{end block} / {parent}
• Built-in variables: {today}, {now}
• XSS-safe: All output HTML-escaped by default
• Graceful degradation: Unparseable expressions preserved as literal text

Extension Points

from pyrx_nlt import NLTRenderer, EventStore, TemplateLoader

class MyEventStore:
    """Implement to look up historical events for named event resolution."""
    async def get_latest(self, contact_id: str, event_name: str) -> dict | None:
        ...

class MyTemplateLoader:
    """Implement for template inheritance ({extends "base.html"})."""
    def load(self, template_name: str) -> str | None:
        ...

renderer = NLTRenderer(
    contact=contact_data,
    event_store=MyEventStore(),
    template_loader=MyTemplateLoader(),
)

Jinja2 Migration

Built-in bidirectional converter for migrating from Jinja2/MoEngage templates:

from pyrx_nlt.converter import convert_jinja2_to_nlt, convert_nlt_to_jinja2, detect_template_language

nlt_template, result = convert_jinja2_to_nlt(jinja2_template)
print(f"Converted {result.count} expressions")

language = detect_template_language(template)  # "nlt", "jinja2", "mixed", or "none"

License

MIT