unimodpy 0.1.1

Python library for parsing and querying the UNIMOD mass spectrometry modifications database.

unimodpy

Python library for parsing and querying the UNIMOD mass spectrometry modifications database.

• Zero dependencies
• Bundled UNIMOD data (1,552 entries) — works offline out of the box
• Typed, immutable data models (py.typed / PEP 561)

Installation

pip install unimodpy

Or with uv:

uv add unimodpy

Requires Python 3.12+. No third-party dependencies.

Quick Start

import unimodpy

# Load the bundled UNIMOD database (no file path needed)
db = unimodpy.load()

# Look up by ID
acetyl = db.get_by_id(1)          # integer
acetyl = db.get_by_id("UNIMOD:1") # UNIMOD accession string
acetyl = db["UNIMOD:1"]           # subscript notation

# Look up by name (case-insensitive)
phospho = db.get_by_name("Phospho")

# Full-text search across name, definition, and synonyms
hits = db.search("glycosyl")

print(acetyl)
# UNIMOD:1  Acetyl
#   Acetylation.
#   Formula  : C2H2O
#   Mass     : +42.010565 Da (mono)  +42.0373 Da (avg)
#   Sites (9):
#     1: K @ Anywhere [Post-translational]
#     ...

Refreshing from unimod.org

# Download the latest OBO and use it immediately
db = unimodpy.load(refresh=True)

# Or just download the file
path = unimodpy.download()                        # ~/.cache/unimodpy/UNIMOD.obo
path = unimodpy.download("/my/dir/UNIMOD.obo")    # custom destination

Loading a Custom File

db = unimodpy.load("/path/to/UNIMOD.obo")
# or low-level:
db = unimodpy.parse_obo("/path/to/UNIMOD.obo")

Working with Entries

Each UnimodEntry is a frozen dataclass:

entry = db.get_by_name("Carbamidomethyl")

entry.id                  # int — UNIMOD accession number
entry.name                # str
entry.delta_mono_mass     # float — monoisotopic mass shift in Da
entry.delta_avge_mass     # float — average mass shift in Da
entry.proforma_formula    # str — Hill-notation formula, e.g. "C3H5NO"
entry.dict_composition    # dict[str, int] — {"C": 3, "H": 5, "N": 1, "O": 1}
entry.synonyms            # tuple[str, ...] — alternative names
entry.specificities       # tuple[Specificity, ...] — site/position rules

for spec in entry.specificities:
    print(spec.site)            # Site enum, e.g. Site.C ("C")
    print(spec.position)        # Position enum, e.g. Position.ANYWHERE
    print(spec.classification)  # Classification enum
    for nl in spec.neutral_losses:
        print(nl.mono_mass, nl.proforma_formula)

Enums

Site, position, and classification values are typed StrEnum members:

from unimodpy import Site, Position, Classification

ptm_sites = [
    spec for spec in entry.specificities
    if spec.classification == Classification.POST_TRANSLATIONAL
    and spec.position == Position.ANYWHERE
]

API Overview

Symbol	Description
load(source=None, *, refresh=False)	Load the database. No args -> bundled file. refresh=True -> download first.
download(dest=None)	Download latest OBO from unimod.org; returns Path.
parse_obo(path)	Low-level: parse any OBO file at path.
UnimodDatabase	Iterable collection with get_by_id, get_by_name, search, __getitem__.
UnimodEntry	Frozen dataclass for one modification term.
Specificity	Frozen dataclass for one site/position rule.
NeutralLoss	Frozen dataclass for one neutral loss.
Site	StrEnum of amino acid residues and termini.
Position	StrEnum of sequence position constraints.
Classification	StrEnum of modification classes.

Development

just install   # install dependencies with uv
just lint      # ruff check
just format    # ruff format
just ty        # ty type check
just test      # pytest
just check     # lint + type check + test

Related Projects

Package	Description
uniprotptmpy	Parse and query the UniProt PTM controlled vocabulary
psimodpy	Parse and query the PSI-MOD protein modification ontology

License

MIT