get extension

Basic data handling: PathGetExtension ("get extension") does exactly one thing: it pulls the file extension off a path and hands it back to you, dot included. photo.png → .png, archive.tar.gz → .gz, noext → "". That's the whole node, and it's genuinely handy when your workflow needs to know what kind of file it's about to touch.

The concrete case: you've globbed a folder of images with PathGlob or listed it with PathListDir, and you want to branch - feed PNGs into one path, JPEGs into another, or skip anything that isn't a .png before it reaches a loader. Compare the extension output against a string in a comparison node (this same pack's "StringComparison" is a natural fit) and you've got a format filter without touching a single regex. It's also useful before a save: check what extension a filename already has so you don't end up with out.png.jpg.

How it works

The implementation is a call to Python's os.path.splitext(path) and taking the second element. That means the behavior is Python's behavior, which is worth knowing on two edges:

• Only the last extension is returned. image.tar.gz gives .gz, not .tar.gz. If you need the middle extension, that's not what this node does.
• No extension → empty string. Files without a dot return "", so your comparison branches on emptiness, not on a sentinel.
• Hidden files are a small trap: .gitignore returns .gitignore under splitext's rules on some platforms because the whole name starts with a dot. Edge case, but it's the kind of thing that makes you double-take in a filter.

Inputs and outputs

• path (STRING, default "") - the filename or full path you're inspecting.
• extension (STRING) - the extension including the leading dot, or "" if there is none.

Installing it

Ships in Basic data handling, the dependency-free pack from StableLlama. Install via ComfyUI Manager (search "Basic data handling") and restart, or:

cd ComfyUI/custom_nodes
git clone https://github.com/StableLlama/ComfyUI-basic_data_handling

Restart after. No models, no extra pip packages - ComfyUI already provides the Python stdlib this node runs on.

Where it bites

Nothing exotic here, but two habits save grief. First, remember the output includes the dot - compare against .png, not png. Second, the empty-string result for extensionless files: if you're building a default extension in, test for "" explicitly rather than assuming something came back. Beyond that, it's a small, predictable utility that does what it says and stays out of the way. That's the whole point of a pack like this.