"Do one thing and do it well." — Peter H. Salus / Doug McIlroy, core Unix principle

"Simple is better than complex." — Zen of Python

String Constructor (Text-Formatting) nodes

... for ComfyUI.

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TL;DR

There's already a plenty of string-formatting nodes for ComfyUI. But this node pack takes a different approach:

• Build your dictionary of available text chunks once. Pass it further as a single line (bus/pipe design).
• Easily reuse these sub-strings to build many variations of a prompt as needed.
• It's especially handy for regional prompting (aka area composition).
• 
• ...
• PROFIT!

The main String Formatter node

It expects one input with a full "library" (dictionary) of all the named strings you might need, and it lets you use them in a prompt - any of them (or none at all), in any order, anywhere inside text template - using python's string formatting syntax... Don't panic! All the unfamiliar programming terms are explained below.

But the main point is, you don't need to fiddle around connecting a bunch of wires every time you'd like to build another prompt, compiled from the same parts. There's just a single node, single input (with all the available text pieces contained within it), single text field - and that's it.

Note

Unlike many other (giant uber-mega) node packs, this one strictly adheres to the modular philosophy: it's minimal and self-sufficient. It's designed to only do string formatting and nothing else.

Dictionary

For those unfamiliar, dictionary is a special datatype, which can contain a bunch of individual values (as many as you need), each of which accessible with its own unique name (key). For our purposes, it can be understood as a simple "search & replace" table. So, you prepare a bunch of distinct parts of the prompt, you name them and then you can reference any of them individually.

For example, in the screenshot shown above, this is the dictionary we get in the end (as the Preview node confirms):

Chunk Name (key)	Chunk Text (value)
model_prefix	score_9, score_8_up, score_7_up
char1_short	1boy, blond, short hair
char1_long	1boy, smiling, blue eyes, blond, short hair,[NEW LINE HERE] wearing a leather jacket, sitting on a bike

And then, we can do this with the same input dictionary:

Note

The BREAK keyword shown here isn't natively supported by Comfy's CLIP Text Encode. But you can use CLIPTextEncode with BREAK syntax or CLIP Text Encode++ from smZNodes (if you want to fully switch from Comfy's to A1111's way of encoding text).

String-Formatting syntax

The way you "paste" values from the dictionary into your text template is called "string formatting". Its syntax is very simple:

• You just put your {key_name} inside curly braces (no spaces between) - and voila! When the prompt template gets formatted, this pattern will be replaced with the actual sub-string.
  • For your convenience, the string-formatting node itself can show the actual output.
• Also keep in mind, that while naming your sub-strings, you must follow the same restrictions python imposes on any variable names: only ASCII letters, digits and underscore are allowed + the name can't start with a digit. So:
  • ✅ valid_name, _other_valid_name_, YetAnother_ValidName___, name4.
  • ❌ wrong name with spaces, wrong-name.with:punctuation, 4name.
  • Don't worry, the node pack will warn you if you type an invalid name.

Note

For advanced users: Internally, just a built-in str.format() is called with keyword arguments from the passed Format-Dict, which is literally just a dict with string keys.

So any formatting patterns are available (like {float_value:.3f}) + Add ANY to Format-Dict node is there for exactly that.

Recursive formatting

It's quite simple in principle yet the most powerful feature of the pack.

When formatting the string, you can let chunks reference each other, which unlocks immense possibilities - like building entire HIERARCHIES of descriptions with various granularity (tailored for different resolutions) or even conditional string formatting for the most advanced users.

Warning

Remember that with great power comes great responsibility!

With a sloppy use, you can create chunks that cross-reference each other in an infinite loop. The node will error out after reaching a high level of recursion (about 1k), so you're safe. But still, you've been warned!

Supporting nodes for Dictionaries

At this point it should be clear that most of the work would be done around preparing the dictionary to use.

The pack provides some utility nodes to build such dict:

• Format-Dict from Text - this node would be enough 99% of the time. It parses a single wall of text and splits it into chunks at empty lines. The first line in each chunk is extracted as key, the rest of the chunk (including new lines, if text continues) is the actual text of this chunk.
• Add String to Format-Dict - similar, but adds only one entry. Useful when you need a value or a key of the dictionary entry to come as input connection from somewhere else.
• Add ANY to Format-Dict (Advanced) similar, but for advanced formatting. It allows you to add not only a string, but literally anything (float, int, etc). The key still must follow the same restrictions.
• Any of these nodes can take another dictionary as input - then they extend/update it.
• Validate Format-Dict - a node that ensures that all the keys in the dictionary are named properly. Useful if you build the dictionary with nodes from other packs (see below) and want to ensure that everything is fine - before passing the dictionary down the line.
• You can design your dict to be intended for updating down the line. Change some keys → get a different prompt with the same template (for example, a more detailed description of a character).
• Don't forget that with recursive formatting, template itself could be a part of the dictionary, too!

These bundled nodes should be enough to start your journey. If you need to do a more advanced stuff with dictionaries, you can look into other node packs specializing on exactly that. Good candidates are:

• Basic Data Handling
• Eugene's Nodes
• WAS Node Suite. Note: this is a mega-pack, over-bloated to my taste. It has nodes to work with dictionaries, but also A TON of other unrelated stuff... and it's known to have dependencies conflicting with other custom nodes.

Supporting nodes for Preview

To debug the dictionary you build, there's a Preview Format-Dict node.

You might also look into the built-in Preview Any node.

Alternatively, Crystools pack has a 🪛 Show any to JSON node, which produces a more readable output. Crystools pack isn't as bloated as WAS' one, but still, it's a multipurpose mega-pack, too.