A lil' TOML parser
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Tomli is a Python library for parsing TOML. It is fully compatible with TOML v1.0.0.
A version of Tomli, the tomllib
module, was added to the standard library in Python 3.11 via PEP 680. Tomli continues to provide a backport on PyPI for Python versions where the standard library module is not available and that have not yet reached their end-of-life.
Tomli uses mypyc to generate binary wheels for most of the widely used platforms, so Python 3.11+ users may prefer it over tomllib
for improved performance. Pure Python wheels are available on any platform and should perform the same as tomllib
.
pip install tomli
import tomli toml_str = """ [[players]] name = "Lehtinen" number = 26 [[players]] name = "Numminen" number = 27 """ toml_dict = tomli.loads(toml_str) assert toml_dict == { "players": [{"name": "Lehtinen", "number": 26}, {"name": "Numminen", "number": 27}] }
import tomli with open("path_to_file/conf.toml", "rb") as f: toml_dict = tomli.load(f)
The file must be opened in binary mode (with the "rb"
flag). Binary mode will enforce decoding the file as UTF-8 with universal newlines disabled, both of which are required to correctly parse TOML.
import tomli try: toml_dict = tomli.loads("]] this is invalid TOML [[") except tomli.TOMLDecodeError: print("Yep, definitely not valid.")
Note that error messages are considered informational only. They should not be assumed to stay constant across Tomli versions.
decimal.Decimal
s from TOML floatsfrom decimal import Decimal import tomli toml_dict = tomli.loads("precision-matters = 0.982492", parse_float=Decimal) assert isinstance(toml_dict["precision-matters"], Decimal) assert toml_dict["precision-matters"] == Decimal("0.982492")
Note that decimal.Decimal
can be replaced with another callable that converts a TOML float from string to a Python type. The decimal.Decimal
is, however, a practical choice for use cases where float inaccuracies can not be tolerated.
Illegal types are dict
and list
, and their subtypes. A ValueError
will be raised if parse_float
produces illegal types.
tomli
/tomllib
compatibility layerPython versions 3.11+ ship with a version of Tomli: the tomllib
standard library module. To build code that uses the standard library if available, but still works seamlessly with Python 3.6+, do the following.
Instead of a hard Tomli dependency, use the following dependency specifier to only require Tomli when the standard library module is not available:
tomli >= 1.1.0 ; python_version < "3.11"
Then, in your code, import a TOML parser using the following fallback mechanism:
import sys if sys.version_info >= (3, 11): import tomllib else: import tomli as tomllib tomllib.loads("['This parses fine with Python 3.6+']")
No.
The tomli.loads
function returns a plain dict
that is populated with builtin types and types from the standard library only. Preserving comments requires a custom type to be returned so will not be supported, at least not by the tomli.loads
and tomli.load
functions.
Look into TOML Kit if preservation of style is what you need.
dumps
, write
or encode
function?Tomli-W is the write-only counterpart of Tomli, providing dump
and dumps
functions.
The core library does not include write capability, as most TOML use cases are read-only, and Tomli intends to be minimal.
TOML type | Python type | Details |
---|---|---|
Document Root | dict | |
Key | str | |
String | str | |
Integer | int | |
Float | float | |
Boolean | bool | |
Offset Date-Time | datetime.datetime | tzinfo attribute set to an instance of datetime.timezone |
Local Date-Time | datetime.datetime | tzinfo attribute set to None |
Local Date | datetime.date | |
Local Time | datetime.time | |
Array | list | |
Table | dict | |
Inline Table | dict |
The benchmark/
folder in this repository contains a performance benchmark for comparing the various Python TOML parsers.
Below are the results for commit 0724e2a.
foo@bar:~/dev/tomli$ python --version Python 3.12.7 foo@bar:~/dev/tomli$ pip freeze attrs==21.4.0 click==8.1.7 pytomlpp==1.0.13 qtoml==0.3.1 rtoml==0.11.0 toml==0.10.2 tomli @ file:///home/foo/dev/tomli tomlkit==0.13.2 foo@bar:~/dev/tomli$ python benchmark/run.py Parsing data.toml 5000 times: ------------------------------------------------------ parser | exec time | performance (more is better) -----------+------------+----------------------------- rtoml | 0.647 s | baseline (100%) pytomlpp | 0.891 s | 72.62% tomli | 3.14 s | 20.56% toml | 6.69 s | 9.67% qtoml | 8.27 s | 7.82% tomlkit | 56.1 s | 1.15%
foo@bar:~/dev/tomli$ python benchmark/run.py Parsing data.toml 5000 times: ------------------------------------------------------ parser | exec time | performance (more is better) -----------+------------+----------------------------- rtoml | 0.668 s | baseline (100%) pytomlpp | 0.893 s | 74.81% tomli | 1.96 s | 34.18% toml | 6.64 s | 10.07% qtoml | 8.26 s | 8.09% tomlkit | 52.9 s | 1.26%