ufoLib2

0.18.1 verified Fri May 01 auth: no python

ufoLib2 is a UFO font processing library for reading, writing, and manipulating Unified Font Object (UFO) files. It provides Python objects for font, layer, glyph, and other UFO structures with lazy loading and efficient serialization. Current version: 0.18.1. Requires Python >=3.9. Maintained by the fonttools project; release cadence is irregular with several minor releases per year.

pip install ufoLib2

Common errors

error ModuleNotFoundError: No module named 'ufoLib2' ↓

cause Library not installed.

fix

pip install ufoLib2

error AttributeError: module 'ufoLib2' has no attribute 'Glyph' ↓

cause Glyph is not exported at package level.

fix

from ufoLib2.objects import Glyph

error TypeError: save() takes 1 positional argument but 2 were given ↓

cause Trying to save with a file path as argument without keyword? Actually save only takes the path as positional.

fix

font.save('/path/to/font.ufo')

error ufoLib2.errors.UFOError: Invalid UFO version: 3 ↓

cause UFO file has format spec version that is not supported or malformed.

fix

Ensure the UFO is valid; check ufo/lib/formatversion.txt. ufoLib2 supports UFO v3 and v2.

error ImportError: cannot import name 'Font' from 'ufoLib2.objects' (unknown location) ↓

cause Wrong import path or outdated version.

fix

Use 'from ufoLib2 import Font' instead.

Warnings

breaking Python 3.8 support dropped in v0.18.0. Use Python >=3.9. ↓

fix Upgrade Python to 3.9 or later.

deprecated The 'fs' module (import fs) will be removed; replaced with tempfile.TemporaryDirectory. Do not rely on fs internals. ↓

fix Replace usage of tempfs with tempfile.TemporaryDirectory.

gotcha Font objects are lazily loaded by default. Modifying glyphs or layers may require explicit loading. ↓

fix Access properties or call .load() to trigger loading. Use Font.open(ufo, lazy=False) to disable lazy loading.

gotcha Saving a UFO creates a directory (UFO format) not a single file. Ensure the save path ends with .ufo and the parent directory exists. ↓

fix Use font.save('/path/to/MyFont.ufo') which creates a directory.

breaking cattrs minimum version upped to 1.10.0 as of v0.13.1. Older cattrs may cause errors with converters. ↓

fix Ensure cattrs >=1.10.0 is installed if using converters extra.

deprecated Use of 'from ufoLib2.objects import Font' is discouraged; prefer 'from ufoLib2 import Font'. ↓

fix Change import to 'from ufoLib2 import Font'.

Install

pip install ufoLib2[converters]

pip install ufoLib2[json,msgpack]

Imports

Font
wrong
```
from ufoLib2.objects import Font
```
correct
```
from ufoLib2 import Font
```
Font is exported at package level since v0.10.0; direct import from objects works but is not recommended.
Glyph
wrong
```
from ufoLib2 import Glyph
```
correct
```
from ufoLib2.objects import Glyph
```
Glyph is not exported at package level; must import from ufoLib2.objects.
Layer
wrong
```
from ufoLib2 import Layer
```
correct
```
from ufoLib2.objects import Layer
```
Layer is not exported at package level; must import from ufoLib2.objects.

Quickstart

Create a new UFO font, set unitsPerEm, save to a temporary directory, then reopen it.

from ufoLib2 import Font

# Create a new font
font = Font()
font.info.unitsPerEm = 1000

# Save to a temporary path (will create .ufo directory)
import tempfile
with tempfile.TemporaryDirectory() as tmpdir:
    ufo_path = f"{tmpdir}/MyFont.ufo"
    font.save(ufo_path)
    print(f"Saved to {ufo_path}")

# Open an existing UFO
font2 = Font.open(ufo_path)
print(font2.info.unitsPerEm)