Monty: Python Made Even Easier
Monty is the missing complement to Python. It implements supplementary
utilities that are not part of the standard library: transparent support for
compressed files, JSON/YAML/msgpack serialization of arbitrary objects, design
patterns such as cached_class, deprecation helpers, and many more.
Python comes with "batteries included", but in building several large scientific frameworks (most notably pymatgen), we found ourselves repeatedly writing the same small utilities. Monty collects these into a single, well-tested, dependency-light library. Where the standard library has since caught up, Monty delegates to it.
Monty supports Python 3.11+.
Installation
pip install monty
# or
uv add monty
Optional extras pull in dependencies for specific features:
| Extra | Enables |
|---|---|
json |
Serialization of numpy, pandas, pint, pydantic, torch and bson objects |
serialization |
msgpack support in dumpfn/loadfn |
multiprocessing |
imap_tqdm progress bars |
dev |
IPython-based install_excepthook |
optional |
All of the above |
pip install "monty[optional]"
Highlights
Transparent compressed I/O. zopen opens plain, .gz, .bz2, .xz and
.lzma files with one call; reverse_readline reads large files from the end.
from monty.io import reverse_readline, zopen
with zopen("OUTCAR.gz", mode="rt", encoding="utf-8") as f:
for line in reverse_readline(f):
if "TOTAL-FORCE" in line:
break
Serialization of arbitrary objects. Subclass MSONable to get
as_dict()/from_dict() and JSON round-tripping for free; dumpfn/loadfn
pick the format (JSON, JSON lines, YAML, msgpack) and compression from the
file extension.
from monty.json import MSONable
from monty.serialization import dumpfn, loadfn
class Calculation(MSONable):
def __init__(self, name: str, energy: float):
self.name = name
self.energy = energy
dumpfn(Calculation("relax", -3.42), "calc.json.gz")
calc = loadfn("calc.json.gz") # -> Calculation instance
Scratch directories. ScratchDir runs a block in a temporary directory
and copies results back on exit.
from monty.tempfile import ScratchDir
with ScratchDir(".", copy_from_current_on_enter=True, copy_to_current_on_exit=True):
... # run an expensive calculation
Development helpers. Mark deprecations with an optional removal deadline, and guard code paths on optional dependencies.
from monty.dev import deprecated, requires
try:
import torch
except ImportError:
torch = None
@deprecated(replacement="new_func", deadline=(2028, 1, 1))
def old_func(): ...
@requires(torch is not None, "torch is required for this function.")
def train(): ...
Other modules include monty.design_patterns (cached_class, singleton),
monty.functools (lazy_property, return_if_raise, timeout),
monty.shutil (compress_dir, decompress_dir, gzip_dir),
monty.os.path (zpath, find_exts), monty.re (regrep) and
monty.collections (frozendict, AttrDict, tree).
See the official docs for the full API.
Development
git clone https://github.com/materialyzeai/monty.git
cd monty
uv sync --all-extras
uv run pytest
uv run ruff check src && uv run ruff format src
uv run mypy -p monty
1 maintainer
Metadata
1 maintainer
Release files for monty 2026.10.21
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