pptx-editor

name

pptx-editor

description

Edit, update, and add slides to PowerPoint (.pptx) files using python-pptx. Use this skill whenever the user wants to modify a presentation - adding slides, editing text, changing styling, reordering slides, inserting links, or fixing design consistency. Trigger on any mention of "slide", "presentation", "PowerPoint", "pptx", "deck", "add a slide", "update the slide", "fix the slides", "last slide", "thank you slide", or any request involving .pptx files - even if the user just references a .pptx path without explicitly saying "edit".

PPTX Editor

Edit PowerPoint files programmatically using python-pptx while preserving visual consistency with the existing deck.

Why this skill exists

PowerPoint editing through code is error-prone because small mismatches in background color, font inheritance, shape positioning, or line styling make new slides look obviously wrong next to existing ones. This skill enforces a "inspect first, match exactly" workflow that prevents those mismatches.

Core workflow

Every PPTX edit follows three phases: Inspect, Edit, Verify. Never skip the inspect phase - it is what prevents visual mismatches.

Phase 1: Inspect the existing deck

Before making any changes, run the inspect script to extract the deck's design system. This is non-negotiable because presentations vary wildly in how they're built - some use layouts, some use manual shapes, some mix both.

python3 .claude/skills/pptx-editor/scripts/inspect-deck.py <path-to-pptx>

The script extracts every shape, text style, color, position, and font across all slides, then prints a design token summary at the end.

From this output, build a mental model of the deck's design tokens:

Token	What to capture	Why it matters
Background	Solid color RGB or theme reference	New slides without this look white against dark decks
Accent color	The color used for bars, separators, labels	Usually one dominant accent throughout
Heading style	Font size, bold, color, position	Titles must match exactly
Body style	Font size, bold/None, color	Subtle: bold=None is different from bold=False
Font typeface	Explicit name or THEME inheritance	If existing slides use THEME, new slides must NOT set font.name
Decorative shapes	Top bars, separators - exact position, size, fill, line style	These define the visual rhythm of the deck
Text positions	Left margin, top positions for titles, bodies, footers	Consistent alignment across slides

Phase 2: Edit the deck

Build new or modified slides using the exact values from Phase 1.

Critical rules:

1. Set the slide background explicitly. The Blank layout does not inherit the master slide background in python-pptx. Always set it:

   slide.background.fill.solid()
   slide.background.fill.fore_color.rgb = RGBColor(0x0D, 0x0D, 0x0D)
   

2. Match font inheritance. If existing slides use theme fonts (no explicit typeface), do NOT set font.name on new text. Setting it forces an explicit typeface that may render differently:

   # CORRECT - inherits theme font
   run = p.add_run()
   run.text = "Hello"
   run.font.size = Emu(457200)
   run.font.bold = True
   run.font.color.rgb = RGBColor(0xFF, 0xFF, 0xFF)
   # Do NOT set run.font.name
   
   # WRONG - overrides theme font
   run.font.name = "Calibri"  # Don't do this if originals use theme
   

3. Reproduce decorative shapes exactly. Copy the position, size, fill color, and line style from the inspection. Pay special attention to:

   # Line style must match - most decks use background (invisible) lines
   shape.line.fill.background()
   shape.line.width = 0
   

4. Use Emu units consistently. The inspection gives values in EMUs. Use them directly - do not convert to Inches or Pt and back, because rounding errors accumulate.

5. Preserve bold=None vs bold=True vs bold=False. In python-pptx, None means "inherit from style", False means "explicitly not bold", and True means "explicitly bold". Match what existing slides use.

6. Add hyperlinks correctly. Use run.hyperlink.address, not shape-level links:

   run = p.add_run()
   run.text = "linkedin.com/in/someone"
   run.font.size = Emu(228600)
   run.font.color.rgb = WHITE
   run.hyperlink.address = 
   

Phase 3: Verify

After saving, run a verification script that compares the new slides against existing ones:

# Check that new slides match the design system
for idx in [<new_slide_indices>]:
    slide = prs.slides[idx]
    bg_color = slide.background.fill.fore_color.rgb if slide.background.fill.type else "MISSING"
    print(f"Slide {idx+1}: background={bg_color}")

Confirm:

• Background color matches existing slides
• Top decorative shapes are present with correct position/size/color
• Text colors and sizes match equivalent elements on other slides
• No explicit font names set when originals use theme fonts

Common operations

Adding slides to the end

Use prs.slides.add_slide(layout). Always use the same layout as existing slides (inspect first to find which one).

Editing text on existing slides

Find the shape by name or by iterating, then modify shape.text_frame.paragraphs[n].runs[m].

Reordering slides

python-pptx does not have a native reorder API. To move a slide, you need to manipulate the XML directly by reordering elements in prs.slides._sldIdLst.

Changing styling across all slides

Use replace_all-style loops. Extract the current value first to avoid changing things that shouldn't change.

Dependencies

Requires python-pptx. Install with:

pip3 install python-pptx

Reference

• scripts/inspect-deck.py - Run this in Phase 1 to extract design tokens from any PPTX file.
• references/design-tokens-checklist.md - Copy-paste checklist to fill in during the inspect phase.