ufo2ft

3.7.1 verified Mon Apr 27 auth: no python

A Python library that compiles UFO (Unified Font Object) sources into OpenType font binaries (.otf and .ttf) using FontTools. Version 3.7.1 requires Python >=3.10. It bridges UFO data structures with FontTools' font compilation pipeline, supporting features like Mark-to-Mark positioning, kern feature generation, and variable font instantiation. Release cadence is irregular with patches every few months.

pip install ufo2ft

Common errors

error ModuleNotFoundError: No module named 'ufo2ft' ↓

cause ufo2ft is not installed, or installed in a different Python environment.

fix

Run 'pip install ufo2ft' in the correct environment.

error ufo2ft.errors.UFO2FTError: missing glyphs in some masters while processing ↓

cause Variable font compilation with inconsistent glyph sets across masters.

fix

Ensure all master UFOs contain the same set of glyphs (including empty ones if necessary).

error AttributeError: module 'ufo2ft' has no attribute 'compileInterpolatable' ↓

cause Wrong function name; the correct function is compileInterpolatableFontFromUFOs.

fix

Use 'from ufo2ft import compileInterpolatableFontFromUFOs'.

Warnings

breaking Python 3.9 dropped as of v3.7.0; requires Python >=3.10. ↓

fix Upgrade to Python 3.10 or higher.

breaking In v3.6.8, dependencies were pinned to exact versions, causing clashes. This was fixed in v3.6.9. ↓

fix Upgrade to v3.6.9 or later, or avoid pinning ufo2ft with exact constraints.

deprecated Some internal modules like ufo2ft.outlineCompiler may change; rely on stable public API (compileOTF, compileTTF, compileInterpolatableFontFromUFOs). ↓

fix Use top-level imports from ufo2ft package.

gotcha ufo2ft works with both defcon and ufoLib2 for UFO objects, but v3.7.0 made neither strictly required. If using defcon, ensure it's installed separately. ↓

fix Install defcon explicitly if needed: pip install defcon.

gotcha When compiling variable fonts, ensure all master UFOs have the same glyph set and consistent outlines; otherwise compilation may fail silently or produce incorrect data. ↓

fix Validate master UFOs before compiling with compileInterpolatableFontFromUFOs().

Imports

compileInterpolatableFontFromUFOs
wrong
```
from ufo2ft.compilers import compileInterpolatableFontFromUFOs
```
correct
```
from ufo2ft import compileInterpolatableFontFromUFOs
```
Top-level import is preferred; direct compiler import may break if internal structure changes.
compileOTF
```
from ufo2ft import compileOTF
```
compileTTF
```
from ufo2ft import compileTTF
```

Quickstart

Compile a single UFO into an OpenType font file.

from ufo2ft import compileOTF
from fontTools.ufoLib import UFOReader

# Replace with actual path to your .ufo
path = "path/to/font.ufo"
reader = UFOReader(path)
font = compileOTF(reader)
font.save("output.otf")
print("OpenType font saved.")