PPTX Authoring

PPTX Authoring

Intro

Use python-pptx to generate PowerPoint files programmatically. Always start from a template PPTX to inherit brand fonts, colors, and slide layouts. One idea per slide — each slide should have a single, clear takeaway expressed in the title. Use charts for quantitative data and images for visual evidence; avoid bullet-heavy text slides.

Overview

Setup

# /// script
# dependencies = ["python-pptx"]
# ///
from pptx import Presentation
from pptx.util import Inches, Pt, Emu
from pptx.dml.color import RGBColor
from pptx.enum.text import PP_ALIGN

prs = Presentation()                          # blank (10×7.5 in widescreen)
prs = Presentation("brand_template.pptx")    # or from a template

Install with uv add python-pptx or pip install python-pptx.

Slide layouts

Every presentation has a slide master with named layouts. List available layouts before picking one:

for i, layout in enumerate(prs.slide_layouts):
    print(i, layout.name)
# Common: 0=Title Slide, 1=Title and Content, 2=Title Only,
#         5=Blank, 6=Content with Caption

Add a slide and populate its placeholders:

layout = prs.slide_layouts[1]   # "Title and Content"
slide = prs.slides.add_slide(layout)

title = slide.shapes.title
title.text = "Slide Title — the Takeaway"

body = slide.placeholders[1]
tf = body.text_frame
tf.text = "First bullet"
tf.add_paragraph().text = "Second bullet"

Placeholder indices vary by template. Inspect with:

for ph in slide.placeholders:
    print(ph.placeholder_format.idx, ph.name)

Text boxes and formatting

from pptx.util import Inches, Pt
txBox = slide.shapes.add_textbox(Inches(1), Inches(1.5), Inches(8), Inches(1))
tf = txBox.text_frame
tf.word_wrap = True

p = tf.paragraphs[0]
p.text = "Label"
p.font.size = Pt(18)
p.font.bold = True
p.font.color.rgb = RGBColor(0x1F, 0x49, 0x7D)
p.alignment = PP_ALIGN.LEFT

Charts

from pptx.chart.data import ChartData
from pptx.enum.chart import XL_CHART_TYPE

chart_data = ChartData()
chart_data.categories = ["Q1", "Q2", "Q3", "Q4"]
chart_data.add_series("Revenue", (1.2, 1.5, 1.8, 2.1))

x, y, cx, cy = Inches(1), Inches(2), Inches(8), Inches(4)
chart = slide.shapes.add_chart(
    XL_CHART_TYPE.COLUMN_CLUSTERED, x, y, cx, cy, chart_data
).chart

chart.has_legend = True
chart.has_title = True
chart.chart_title.text_frame.text = "Quarterly Revenue ($M)"

Common chart types: COLUMN_CLUSTERED, BAR_CLUSTERED, LINE, PIE, AREA, XY_SCATTER. Prefer column/bar for comparisons, line for trends, and scatter for correlations.

Tables

rows, cols = 3, 3
table = slide.shapes.add_table(rows, cols, Inches(1), Inches(2),
                                Inches(8), Inches(2)).table

table.cell(0, 0).text = "Metric"
table.cell(0, 1).text = "Value"
table.cell(0, 2).text = "Change"

# Column widths
table.columns[0].width = Inches(3)
table.columns[1].width = Inches(2.5)
table.columns[2].width = Inches(2.5)

Images

slide.shapes.add_picture("screenshot.png", Inches(1), Inches(2),
                          width=Inches(4))

# From BytesIO (no disk write)
from io import BytesIO
slide.shapes.add_picture(image_stream, left, top, width=Inches(4))

Saving

prs.save("deck.pptx")

# To BytesIO
buf = BytesIO()
prs.save(buf)
buf.seek(0)

Slide design principles

• One takeaway per slide. The title states the insight; the body provides evidence. Avoid "Section 3" or "Data" as slide titles.
• 5×5 rule. At most 5 bullets, at most 5 words each. Prefer one key data point over three mediocre ones.
• Slide count. Aim for 1 slide per minute of talk time; executive briefings: 10-15 slides maximum.
• Sequence. Title → Problem/Context → Key Data → Insight → Recommendation → Next Steps. Each slide answers one question the previous raised.
• Consistent layout. Use slide layouts from the template — do not position elements by eye. Grid-aligned elements look professional; manually-placed text boxes drift.

Gotchas

Agent-specific failure modes — provider-neutral pause-and-self-check items:

• Starting from a blank Presentation() instead of a brand template. A blank deck uses python-pptx's default fonts and a white background. Corporate and client decks must open from the organization's template PPTX to inherit brand colors, fonts, and slide layouts. Always use Presentation("template.pptx") when the output will be shared.
• Using placeholder index 1 without verifying the layout. Placeholder indices vary by slide layout and template. Hardcoding slide.placeholders[1] for the body works on the default "Title and Content" layout but fails silently on others, placing text in the wrong element or raising an IndexError. Always inspect ph.placeholder_format.idx and ph.name for the target layout.
• Putting the same text in every slide title. Titles like "Data", "Results", or "Analysis" describe the format, not the insight. Slide titles should state the takeaway so an executive reading only the titles can follow the narrative. Rewrite generic titles as findings.
• Adding text boxes instead of using layout placeholders. Manually positioned text boxes do not respect the template's text styles, and they shift when the file is opened on different screen sizes. Use slide.placeholders for content that fits a layout; reserve add_textbox() only for truly free-form annotations.
• Not setting chart title and axis labels. A chart without a title and labeled axes forces the reader to infer context from surrounding text. Every chart must have a descriptive chart_title and, for all axes with units, an axis title set via chart.value_axis.axis_title.
• Saving to the same path as the template. prs.save("brand_template.pptx") overwrites the template, making the next generation run produce corrupt output or inherit changes from the previous run. Always save to a distinct output path.
• Not opening the generated PPTX in PowerPoint or LibreOffice before delivery. python-pptx can produce XML that opens without error but renders incorrectly — font fallbacks, missing charts, mispositioned images. Always open the output file visually before sharing it.

Full reference

Shape positioning constants

All positions and sizes in python-pptx are in EMUs (English Metric Units). Helpers: Inches(n) = n×914400 EMUs, Pt(n) = n×12700 EMUs, Cm(n) = n×360000 EMUs.

Widescreen (16:9) slide: 12192000 × 6858000 EMU (9.14 × 5.14 in). Standard (4:3) slide: 9144000 × 6858000 EMU.

Custom slide size

from pptx.util import Inches
prs.slide_width  = Inches(13.33)   # widescreen 16:9
prs.slide_height = Inches(7.5)

Speaker notes

notes_slide = slide.notes_slide
notes_slide.notes_text_frame.text = "Talking points for this slide..."

Duplicate a slide

python-pptx has no built-in slide-copy API. The pattern:

import copy
from lxml import etree

template_slide = prs.slides[0]
xml_str = etree.tostring(template_slide._element)
new_el = etree.fromstring(xml_str)
prs.slides._sldIdLst.append(new_el)

Animation

python-pptx does not support animation. To add animations, inject OOXML directly into the slide's _element or use a macro-enabled PPTM as the template.

Conversion to PDF

libreoffice --headless --convert-to pdf deck.pptx

Or use the Google Slides API to import and export as PDF.