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diff --git a/README.md b/README.md new file mode 100644 index 0000000..2c856b4 --- /dev/null +++ b/README.md @@ -0,0 +1,181 @@ +[](https://github.com/hukkin/tomli/actions?query=workflow%3ATests+branch%3Amaster+event%3Apush) +[](https://codecov.io/gh/hukkin/tomli) +[](https://pypi.org/project/tomli) + +# Tomli + +> A lil' TOML parser + +**Table of Contents** *generated with [mdformat-toc](https://github.com/hukkin/mdformat-toc)* + +<!-- mdformat-toc start --slug=github --maxlevel=6 --minlevel=2 --> + +- [Intro](#intro) +- [Installation](#installation) +- [Usage](#usage) + - [Parse a TOML string](#parse-a-toml-string) + - [Parse a TOML file](#parse-a-toml-file) + - [Handle invalid TOML](#handle-invalid-toml) + - [Construct `decimal.Decimal`s from TOML floats](#construct-decimaldecimals-from-toml-floats) +- [FAQ](#faq) + - [Why this parser?](#why-this-parser) + - [Is comment preserving round-trip parsing supported?](#is-comment-preserving-round-trip-parsing-supported) + - [Is there a `dumps`, `write` or `encode` function?](#is-there-a-dumps-write-or-encode-function) + - [How do TOML types map into Python types?](#how-do-toml-types-map-into-python-types) +- [Performance](#performance) + +<!-- mdformat-toc end --> + +## Intro<a name="intro"></a> + +Tomli is a Python library for parsing [TOML](https://toml.io). +Tomli is fully compatible with [TOML v1.0.0](https://toml.io/en/v1.0.0). + +## Installation<a name="installation"></a> + +```bash +pip install tomli +``` + +## Usage<a name="usage"></a> + +### Parse a TOML string<a name="parse-a-toml-string"></a> + +```python +import tomli + +toml_str = """ + gretzky = 99 + + [kurri] + jari = 17 + """ + +toml_dict = tomli.loads(toml_str) +assert toml_dict == {"gretzky": 99, "kurri": {"jari": 17}} +``` + +### Parse a TOML file<a name="parse-a-toml-file"></a> + +```python +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. + +### Handle invalid TOML<a name="handle-invalid-toml"></a> + +```python +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. + +### Construct `decimal.Decimal`s from TOML floats<a name="construct-decimaldecimals-from-toml-floats"></a> + +```python +from decimal import Decimal +import tomli + +toml_dict = tomli.loads("precision-matters = 0.982492", parse_float=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. + +## FAQ<a name="faq"></a> + +### Why this parser?<a name="why-this-parser"></a> + +- it's lil' +- pure Python with zero dependencies +- the fastest pure Python parser [\*](#performance): + 15x as fast as [tomlkit](https://pypi.org/project/tomlkit/), + 2.4x as fast as [toml](https://pypi.org/project/toml/) +- outputs [basic data types](#how-do-toml-types-map-into-python-types) only +- 100% spec compliant: passes all tests in + [a test set](https://github.com/toml-lang/compliance/pull/8) + soon to be merged to the official + [compliance tests for TOML](https://github.com/toml-lang/compliance) + repository +- thoroughly tested: 100% branch coverage + +### Is comment preserving round-trip parsing supported?<a name="is-comment-preserving-round-trip-parsing-supported"></a> + +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](https://github.com/sdispater/tomlkit) if preservation of style is what you need. + +### Is there a `dumps`, `write` or `encode` function?<a name="is-there-a-dumps-write-or-encode-function"></a> + +[Tomli-W](https://github.com/hukkin/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. + +### How do TOML types map into Python types?<a name="how-do-toml-types-map-into-python-types"></a> + +| 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` | | + +## Performance<a name="performance"></a> + +The `benchmark/` folder in this repository contains a performance benchmark for comparing the various Python TOML parsers. +The benchmark can be run with `tox -e benchmark-pypi`. +Running the benchmark on my personal computer output the following: + +```console +foo@bar:~/dev/tomli$ tox -e benchmark-pypi +benchmark-pypi installed: attrs==19.3.0,click==7.1.2,pytomlpp==1.0.2,qtoml==0.3.0,rtoml==0.7.0,toml==0.10.2,tomli==1.1.0,tomlkit==0.7.2 +benchmark-pypi run-test-pre: PYTHONHASHSEED='2658546909' +benchmark-pypi run-test: commands[0] | python -c 'import datetime; print(datetime.date.today())' +2021-07-23 +benchmark-pypi run-test: commands[1] | python --version +Python 3.8.10 +benchmark-pypi run-test: commands[2] | python benchmark/run.py +Parsing data.toml 5000 times: +------------------------------------------------------ + parser | exec time | performance (more is better) +-----------+------------+----------------------------- + rtoml | 0.901 s | baseline (100%) + pytomlpp | 1.08 s | 83.15% + tomli | 3.89 s | 23.15% + toml | 9.36 s | 9.63% + qtoml | 11.5 s | 7.82% + tomlkit | 56.8 s | 1.59% +``` + +The parsers are ordered from fastest to slowest, using the fastest parser as baseline. +Tomli performed the best out of all pure Python TOML parsers, +losing only to pytomlpp (wraps C++) and rtoml (wraps Rust). |