Generating Model-Bound Financial Decks with python-pptx

This reference describes how to produce a .pptx file on disk using python-pptx for financial decks—pitch decks, IC memos, or earnings notes—where every number traces to a source workbook. The skill is designed for headless environments without Office or MCP for live PowerPoint.

When to Use This Skill

Use this skill when you need to produce a PowerPoint file as an artifact, not a live session. It is appropriate for building financial pitch decks, IC memos, or earnings notes where numbers must be bound to a model workbook. Use it in a headless environment without Office or MCP for live PowerPoint. Every figure on a slide must trace to a specific cell or named range in an Excel model.

Prerequisites

Before using this skill, ensure you have:

A Python environment with python-pptx >=0.6 installed.
openpyxl installed if binding to an Excel model.
An Excel model workbook at ./out/model.xlsx with named ranges or specific cells defined.
The model workbook recalculated before reading (via excel-author recalc helper or manual open/save).
Optional: a firm template at ./templates/firm-template.pptx.
Optional: pre-rendered chart PNGs at ./out/charts/ for embedding.

Installation

Install the required library with:

pip install "python-pptx>=0.6"

Capabilities

The skill can:

Create a .pptx file from Python using python-pptx.
Load a firm template from ./templates/firm-template.pptx if present; otherwise start blank.
Add slides with title and content (title slide, title-only, table, image).
Add tables with headers and data rows.
Embed PNG images (e.g., charts rendered from the model).
Bind deck numbers to an Excel model via openpyxl reading named ranges or cells.
Write output to ./out/<filename>.pptx, creating ./out/ if missing.
Return the relative path of the output file in the final message.

Parameters

template path: Path to firm template file (./templates/firm-template.pptx). If it exists, the deck inherits branded colors, fonts, and master layouts. Optional; if missing, start blank.
model workbook path: Path to the Excel model (./out/model.xlsx) from which to read numbers via named ranges or cells. Optional; if used, must recalc the workbook first.
output filename: Name of the .pptx file to write inside ./out/ (e.g., pitch-aurora.pptx). Required.

Procedure: Create a Pitch Deck Bound to an Excel Model

Follow these steps in order:

Install python-pptx (>=0.6) via pip.
Check if ./templates/firm-template.pptx exists; if yes, load it as Presentation(str(template)), else Presentation().
Create slides using prs.slides.add_slide(prs.slide_layouts[<index>]).
For each slide, set slide.shapes.title.text to a takeaway sentence (one idea per slide).
For a title slide, set slide.placeholders[1].text for the subtitle.
For tables, use slide.shapes.add_table(rows, cols, left, top, width, height) then populate cells.
For embedded charts, use slide.shapes.add_picture(png_path, left, top, width=Inches(8)).
Read model values from ./out/model.xlsx using openpyxl: load_workbook(data_only=True), define a helper to resolve named ranges (wb.defined_names[name], iterate destinations, read cell value).
Recalculate the workbook before reading (use excel-author recalc helper or open/save in Excel) because openpyxl only sees computed values if the sheet was already calculated.
Build slide titles and table content using those values (e.g., f-string with ${value:.2f}).
Ensure every figure footnotes its source, for example: Revenue: $1,250M (Source: model.xlsx, Inputs!C3).
Create ./out/ directory if not exists: Path('./out').mkdir(exist_ok=True).
Save the presentation: prs.save('./out/<filename>.pptx').
Return the relative path of the saved file.

Loading a Template or Starting Blank

The following code loads the firm template if it exists, or starts with a blank presentation:

from pptx import Presentation
from pathlib import Path

template = Path("./templates/firm-template.pptx")
prs = Presentation(str(template)) if template.exists() else Presentation()

Building a Complete Deck

The following example creates a pitch deck with a title slide, valuation summary table, and an embedded chart:

from pptx import Presentation
from pptx.util import Inches, Pt
from pptx.dml.color import RGBColor
from pathlib import Path

template = Path("./templates/firm-template.pptx")
prs = Presentation(str(template)) if template.exists() else Presentation()

# Title slide
slide = prs.slides.add_slide(prs.slide_layouts[0])
slide.shapes.title.text = "Project Aurora — Strategic Alternatives"
slide.placeholders[1].text = "Preliminary Discussion Materials"

# Valuation summary slide (title-only layout)
slide = prs.slides.add_slide(prs.slide_layouts[5])
slide.shapes.title.text = "Valuation implies $38–$52 per share across methodologies"

# Add a table bound to model outputs
rows, cols = 5, 4
tbl_shape = slide.shapes.add_table(rows, cols,
                                   Inches(0.5), Inches(1.5),
                                   Inches(9), Inches(3))
tbl = tbl_shape.table
headers = ["Methodology", "Low ($)", "Mid ($)", "High ($)"]
for c, h in enumerate(headers):
    tbl.cell(0, c).text = h

# In a real deck, read these from the model workbook with openpyxl
data = [
    ("Trading comps",     "35", "41", "48"),
    ("Precedent M&A",     "39", "45", "52"),
    ("DCF (base)",        "36", "43", "51"),
    ("LBO (10% IRR)",     "33", "38", "44"),
]
for r, row in enumerate(data, start=1):
    for c, val in enumerate(row):
        tbl.cell(r, c).text = val

# Embed a chart rendered from the model
slide = prs.slides.add_slide(prs.slide_layouts[5])
slide.shapes.title.text = "Football field — current price $42"
slide.shapes.add_picture("./out/charts/football_field.png",
                         Inches(1), Inches(1.8), width=Inches(8))

Path("./out").mkdir(exist_ok=True)
prs.save("./out/pitch-aurora.pptx")

In this example, the valuation summary table shows a range from $38 to $52 per share. The football field chart is embedded at the current price of $42. The LBO row uses a 10% IRR assumption. The trading comps methodology shows a low of $35, mid of $41, and high of $48. The precedent M&A row shows a low of $39, mid of $45, and high of $52. The DCF base case shows a low of $36, mid of $43, and high of $51. The LBO row shows a low of $33, mid of $38, and high of $44.

Binding Numbers to an Excel Model

Use openpyxl to read values from the model workbook. The following helper resolves named ranges:

from openpyxl import load_workbook

wb = load_workbook("./out/model.xlsx", data_only=True)
def nr(name):
    """Resolve a named range to its current computed value."""
    rng = wb.defined_names[name]
    sheet, coord = next(rng.destinations)
    return wb[sheet][coord].value

revenue_fy24 = nr("RevenueFY24")
implied_mid  = nr("ImpliedSharePriceBase")

Then use the values in slide titles:

slide.shapes.title.text = f"Implied share price of ${implied_mid:.2f} (base case)"

Every number on a slide must trace to the model workbook (sheet and cell). Never transcribe from memory or summary.

Embedding Charts

Use PNG-from-model for charts when fidelity matters. Native pptx.chart charts are fragile and may not match firm conventions. Embed a chart with:

from pptx.util import Inches
slide.shapes.add_picture("./out/charts/football_field.png",
                         Inches(1), Inches(2),
                         width=Inches(8))

Constraints and Caveats

Output must be written to ./out/<filename>.pptx; create ./out/ if missing.
Return the relative path in the final message.
Every number on a slide must trace to the model workbook (sheet and cell). Never transcribe from memory or summary.
Use PNG-from-model for charts (not native pptx charts) when fidelity matters; native charts are fragile and may not match firm conventions.
This skill only writes a file; never emails, uploads, or posts.
Do not use for live PowerPoint sessions (use Office MCP instead).
Do not use for non-financial slideware (use broader powerpoint skill).
Do not use for decks requiring heavy animation, transitions, or speaker notes (use broader powerpoint skill).
openpyxl only sees computed values if the workbook was already calculated; recalc before reading (use excel-author recalc helper or open/save in Excel).
One idea per slide: the title states the takeaway, the body supports it.

Failure Modes

Missing template file causes fallback to blank presentation (no error).
Model workbook not recalculated before reading yields stale or None values from openpyxl.
Named range not found in workbook raises KeyError when iterating destinations.
Output directory ./out/ not created before save causes FileNotFoundError.
python-pptx not installed or wrong version causes ImportError.
Image file (PNG) not found at specified path causes add_picture to fail.

Slide-Type Checklist for Pitch Decks

A typical pitch deck includes: cover, disclaimer, TOC, situation overview, company snapshot, market context, valuation summary (football field), trading comps detail, precedent transactions detail, DCF summary, illustrative LBO, process considerations, and appendix.

Authoring a Pitch Deck

When authoring a pitch deck, use the pptx-author skill to produce the file. The output filename should reflect the deck type, for example pitch-deck. The final file is saved to ./out/.pptx.

Pptx Author: Build Headless PowerPoint Decks with python-pptx