Working with Slides

Every slide in a presentation is based on a slide layout. Not surprising then that you have to specify which slide layout to use when you create a new slide. Let’s take a minute to understand a few things about slide layouts that we’ll need so the slide we add looks the way we want it to.

Slide layout basics

A slide layout is like a template for a slide. Whatever is on the slide layout “shows through” on a slide created with it and formatting choices made on the slide layout are inherited by the slide. This is an important feature for getting a professional-looking presentation deck, where all the slides are formatted consistently. Each slide layout is based on the slide master in a similar way, so you can make presentation-wide formatting decisions on the slide master and layout-specific decisions on the slide layouts. There can actually be multiple slide masters, but I’ll pretend for now there’s only one. Usually there is.

The presentation themes that come with PowerPoint have about nine slide layouts, with names like Title, Title and Content, Title Only, and Blank. Each has zero or more placeholders (mostly not zero), preformatted areas into which you can place a title, multi-level bullets, an image, etc. More on those later.

The slide layouts in a standard PowerPoint theme always occur in the same sequence. This allows content from one deck to be pasted into another and be connected with the right new slide layout:

  • Title (presentation title slide)
  • Title and Content
  • Section Header (sometimes called Segue)
  • Two Content (side by side bullet textboxes)
  • Comparison (same but additional title for each side by side content box)
  • Title Only
  • Blank
  • Content with Caption
  • Picture with Caption

In python-pptx, these are prs.slide_layouts[0] through prs.slide_layouts[8]. However, there’s no rule they have to appear in this order, it’s just a convention followed by the themes provided with PowerPoint. If the deck you’re using as your template has different slide layouts or has them in a different order, you’ll have to work out the slide layout indices for yourself. It’s pretty easy. Just open it up in Slide Master view in PowerPoint and count down from the top, starting at zero.

Now we can get to creating a new slide.

Adding a slide

Let’s use the Title and Content slide layout; a lot of slides do:

SLD_LAYOUT_TITLE_AND_CONTENT = 1

prs = Presentation()
slide_layout = prs.slide_layouts[SLD_LAYOUT_TITLE_AND_CONTENT]
slide = prs.slides.add_slide(slide_layout)

A few things to note:

  • Using a “constant” value like SLD_LAYOUT_TITLE_AND_CONTENT is up to you. If you’re creating many slides it can be handy to have constants defined so a reader can more easily make sense of what you’re doing. There isn’t a set of these built into the package because they can’t be assured to be right for the starting deck you’re using.
  • prs.slide_layouts is the collection of slide layouts contained in the presentation and has list semantics, at least for item access which is about all you can do with that collection at the moment. Using prs for the Presentation instance is purely conventional, but I like it and use it consistently.
  • prs.slides is the collection of slides in the presentation, also has list semantics for item access, and len() works on it. Note that the method to add the slide is on the slide collection, not the presentation. The add_slide() method appends the new slide to the end of the collection. At the time of writing it’s the only way to add a slide, but sooner or later I expect someone will want to insert one in the middle, and when they post a feature request for that I expect I’ll add an insert_slide(idx, ...) method.

Doing other things with slides

Right now, adding a slide is the only operation on the slide collection. On the backlog at the time of writing is deleting a slide and moving a slide to a different position in the list. Copying a slide from one presentation to another turns out to be pretty hard to get right in the general case, so that probably won’t come until more of the backlog is burned down.

Up next ...

Ok, now that we have a new slide, let’s talk about how to put something on it ...