Custom formatting of reportlab lists

reportlab_list_formatting.py

#!/usr/bin/env python3

import unicodedata
from pathlib import Path
from reportlab.platypus import SimpleDocTemplate, Paragraph, ListFlowable, Spacer
from reportlab.lib.styles import getSampleStyleSheet

output = Path.cwd() / Path(__file__).with_suffix(".pdf").name
doc = SimpleDocTemplate(str(output))

styles = getSampleStyleSheet()
normal = styles["Normal"]
body = styles["BodyText"]
h2 = styles["Heading2"]

def second_tetration(value: str):
    try:
        n = int(value)
        try:
            # Only works up to 9 (i.e. single digits)
            exponent = unicodedata.lookup(unicodedata.name(str(n)).replace("DIGIT", "SUPERSCRIPT"))
        except KeyError:
            exponent = None
        
        if exponent is None:
            return f"{n}^{n} = {n ** n}"
        else:
            return f"{n}{exponent} = {n ** n}"
    except ValueError:
        return value

story = [
    Paragraph("Plain", h2),
    ListFlowable(
        [Paragraph(s, normal) for s in ["One", "Two", "Three"]]
    ),
    
    Paragraph("With a Full Stop (Period)", h2),
    ListFlowable(
        [Paragraph(s, normal) for s in [
            "First element",
            "This is the second element",
        ]],
        bulletFormat="%s.",  # ←
    ),
    
    Paragraph("With a Right Parenthesis", h2),
    ListFlowable(
        [Paragraph(s, normal) for s in [
            "First item",
            "Second one",
        ]],
        bulletType="a",
        bulletFormat="%s)",  # ←
    ),
    Paragraph(
        "Note that we must also change the bulletType here to get a sequence using "
        "letters instead of numbers.",
        body,
    ),
    
    Paragraph("Second Tetration", h2),
    ListFlowable(
        [Paragraph(s, normal) for s in [
            "One to the power one",
            "Two to the power two",
            "Three to the power three",
        ]],
        leftIndent=48,
        bulletFormat=second_tetration,  # ←
    ),
    Paragraph(
        """
        Here the bullet is changed to its second tetration; which is to say 'n to
        the power n'. Unlikely you want this, but a demonstration that your imagination
        is the limit here. Note that to really make use of this functionality you
        will have to play about with fonts and styles to ensure whatever characters
        you're returning have glyphs that can be rendered. Hint: grab a copy of
        <link href="https://www.gnu.org/software/freefont/">GNU FreeFont</link>.
        """,
        body,
    ),

]
doc.build(story)