catslap 1.4.1

Catslap loads JSON input and applies it to document templates to generate final outputs

catslap

catslap is a Python library for automatic document generation from structured JSON data and parameterized templates. It can produce final documents in multiple formats by evaluating directives embedded directly in the templates.

Key features

• Document generation from an input JSON file.
• Support for multiple output formats:
  • Word
  • PowerPoint
  • Excel
  • Plain text
  • HTML
  • JavaScript
• Single or multiple templates:
  • A single file.
  • Multiple files packaged in a ZIP or contained in a directory.
• Ability to limit which template file extensions are processed.
• Expression and logic evaluation with Python semantics.
• Rendering of HTML embedded in JSON data for rich formats (Word and PowerPoint).

General concept

The catslap workflow is:

1. Provide a JSON file with input data.
2. Define one or more templates containing directives.
3. catslap evaluates the directives, accesses the data, and generates the final documents in the desired formats.

Usage example

Example of using the Catslap class directly:

import json
from catslap.catslap import Catslap

with open("data.json", "r", encoding="utf-8") as fh:
  json_map = json.load(fh)

catslap = Catslap(json_map)
catslap.process_dir_or_file(
  template="templates/example.docx",
  output="out/example.docx",
  exts=None,
  verbose=True,
)

CLI usage (quick test)

You can also run catslap from the command line to quickly validate templates. There are sample inputs in the test/ directory.

Examples using the existing test data:

python catslap/catslap.py test/data/Catslap_sales.json test/templates/docx/Catslap_example.docx test/out
python catslap/catslap.py test/data/Catslap_sales.json test/templates test/out -v

Accessing data from templates

JSON data is accessed through expressions delimited by {{ ... }}. Evaluation follows Python behavior as if the JSON were a dict, with the addition of dot-operator access.

Input JSON example

{
  "report_name": "My report",
  "report_data": {
    "name": "BBS Tennesy",
    "account": "0000123",
    "values": [43, 56, 991, 2]
  }
}

Data access examples

{{report_data.account}}
{{report_data.get('account')}}
{{report_data['account']}}

Be careful when using JSON names that match Python tokens to avoid evaluation issues. For example, if you use items inside a JSON object, you cannot access it with dot notation (e.g., data.items), but you can access it with data['items'] or data.get('items').

When a JSON value contains HTML code (starting with an HTML tag), it will be rendered in a rich format when the output document type supports it.

Template directives

Directives are defined using {% ... %} blocks, and each directive must occupy a full paragraph in the template.

Supported directive types

• Loops
• Conditions
• Variable assignment
• Configurations (format-dependent)

Loops

Allow iterating over JSON lists. Syntax:

{% for <name> in <list-expression> %}
...
{% endfor %}

Example:

{% for value in report_data.values %}
  {{value}}
{% endfor %}

Conditions

Allow conditional execution of content blocks. The condition is evaluated as a Python expression.

{% if report_data.account %}
  Valid account
{% elif report_data.account == '0' %}
  Zero account
{% else %}
  Undefined account
{% endif %}

Any number of {% elif <expression> %} branches can follow the {% if %}. The first branch whose condition is true is rendered; the rest are skipped. {% else %} is optional and is rendered only when no previous branch matched.

Variable assignment

Assigns a value to a named variable so it can be reused in subsequent expressions. The value is a Python expression evaluated against the current JSON context.

{% set <name>=<expression> %}

Example:

{% for item in report_data.items %}
  {% set detail=products[item.id] %}
  {{item.id}}  {{detail.name}}  {{detail.price}}
{% endfor %}

The variable lives only within the scope where it is declared:

• Declared inside {% for %} → removed at the end of each iteration.
• Declared inside {% if %} → removed when {% endif %} is reached.
• Declared at the top level → available for the rest of the document.

Style configurations (Word and PowerPoint)

For Word and PowerPoint documents, catslap allows defining how HTML found in JSON data is rendered through style directives. The style directive format is:

{% style <keyword>=<style_name> %}

<keyword> are predefined catslap styles corresponding to HTML styles. <style_name> is the name of the style to use from the styles defined in the Word or PowerPoint template document.

Style configuration example

{% style heading=Heading 1 %}
{% style table_cell=Normal cell %}
{% style table_header=Header cell %}
{% style table_header_bgcolor=#FF0000 %}
{% style table_cell_bgcolor=white %}
{% style table_cell_bgcolor2=#E8E8E8 %}
{% style table_caption=Table caption %}
{% style code=Code %}
{% style codeblock=Codeblock %}
{% style token=Token %}
{% style link_title=LinkTitle %}
{% style link_url=LinkUrl %}
{% style quote=Highlighted quote %}

Supported styles

• heading Defines the style for HTML headings (<H1> to <H6>). If a single style is defined, successive styles are automatically generated with prefixes 2, 3, 4, 5, and 6. By default, the styles are already defined as "Heading1", ..., "Heading6".

• paragraph Defines the style for HTML paragraphs <P>. By default, the "Normal" style is used.

• list_bullet Defines the style for HTML unordered lists <UL>. If a single style is defined, successive styles are automatically generated with prefixes 2, 3, 4, 5, and 6 for successive list indentations. By default, the styles are already defined as "Bullet List1", ..., "Bullet List6".

• list_number Defines the style for HTML ordered lists <OL>. If a single style is defined, successive styles are automatically generated with prefixes 2, 3, 4, 5, and 6 for successive list indentations. By default, the styles are already defined as "Numbered List1", ..., "Numbered List6".

• table_cell Paragraph style inside <TD>. Character formatting defined by the referenced Word style is preserved when rendering cell content.

• table_header Paragraph style inside <TH>. Character formatting defined by the referenced Word style is preserved when rendering header cell content.

• table_header_bgcolor Default background color for table headers.

• table_cell_bgcolor Default background color for table cells.

• table_cell_bgcolor2 Alternate background color for odd rows (optional).

• table_caption Paragraph style for <CAPTION>.

• code Character style for content inside <code>.

• codeblock Paragraph style for <pre> blocks.

• token Paragraph style for <div class="token">.

• link_title Paragraph style for link text.

• link_url Paragraph style for link URLs.

• quote Paragraph style for highlighted quote blocks.

HTML rendering (Word and PowerPoint)

catslap supports interpretation of a subset of HTML to generate rich documents.

Supported tags

• <P>: Paragraphs, with CSS support for:

  • text-align
  • color
  • font-weight
  • font-style
  • text-decoration

• <H1> to <H6>: Chapter headings.

• <OL>, <UL>, <LI>: Ordered and unordered lists.

• <PRE>: Code blocks.

• <BLOCKQUOTE>: Highlighted quotes.

• <CODE>: Inline code.

• <EM>, <I>: Italic.

• <STRONG>, <B>: Bold.

• <U>: Underline.

• <STROKE>: Strikethrough.

• <FONT color="">: Text color (also via CSS color).

• <TABLE>, <TR>, <TD>, <TH>, <CAPTION>, <THEAD>, <TBODY>: Table definition.

• <IMG>: Images.

• <A href="">...</A>: Links.

• <DIV class="<style>">: Apply predefined block styles (token, table_cell, codeblock, etc.).

• <SPAN class="<style>">: Apply character-level styles (only code).

License

MIT License

ChangeLog

1.4.1

• Fixed generation of HTML tables containing empty rows so they no longer break the rendered Word table structure.
• Preserved character styling defined by Word table cell/header styles when rendering content inside table cells.

1.4.0

• New {% elif <expression> %} directive for conditional branching. Any number of elif branches can follow an {% if %}, with only the first matching branch rendered.
• Full directive support for PowerPoint templates: {% for %}, {% if %}, {% elif %}, {% else %}, {% set %}, {% colormap %} now work in .pptx files with the same semantics as Word templates.

1.3.0

• New directive {% set name=value %} for scoped variable assignment. Variables declared inside a for or if block are automatically removed when the block ends; global declarations persist for the whole document.
• Built-in Python functions now available in expressions: len, str, int, float, bool, list, dict, sum, min, max, abs, round, sorted, any, all, isinstance, etc.
• Loop variables declared with for and set are now accessible alongside JSON data in the same expression (e.g. dependencies[name]).
• HTML images with blob: URL scheme (blob:https://host/uuid) are now fetched from the server and embedded directly in the Word document.
• Improved HTML image sizing: dimensions specified as CSS values (e.g. width: 300px) are correctly parsed; images are automatically scaled down to the maximum page width when they exceed it.

1.2.1

• Error fixed with numerated styles (Título1, Título2, ...)

1.2.0

• Supports all css colors
• HTML tables supports character styles and proportional width

1.1.1

• Fixed a bug in HTML tables

1.1.0

• New feature: supports text hightlights
• New directive: 'colormap' to map an html color with other in document generation time
• Style bug fixed

1.0.8

• Re-uploaded by incomplete changes

1.0.7

• Default paragraph, justified
• Bug fixed about tags letter case
• Keep blank lines in

1.0.6

• Word style bug fixed

1.0.5

• Some bugs fixed

1.0.4

• New method for class Catslap: process(self, template_file: str) -> bytes Process template and obtains output document bytes

1.0.3

• Initial release