`!tomllib` --- Parse TOML files
tomllib
Source code: Lib/tomllib
This module provides an interface for parsing TOML 1.1.0 (Tom's Obvious Minimal Language, https://toml.io). This module does not support writing TOML.
3.11 The module was added with support for TOML 1.0.0.
3.15 Added TOML 1.1.0 support. See the What's New <whatsnew315-tomllib-1-1-0> for details.
[!WARNING] Be cautious when parsing data from untrusted sources. A malicious TOML string may cause the decoder to consume considerable CPU and memory resources. Limiting the size of data to be parsed is recommended.
The Tomli-W package <tomli-w> is a TOML writer that can be used in conjunction with this module, providing a write API familiar to users of the standard library marshal and pickle modules.
The TOML Kit package <tomlkit> is a style-preserving TOML library with both read and write capability. It is a recommended replacement for this module for editing already existing TOML files.
This module defines the following functions:
load(fp, /, *, parse_float=float)
Read a TOML file. The first argument should be a readable and binary file object. Return a dict. Convert TOML types to Python using this conversion table <toml-to-py-table>.
parse_float will be called with the string of every TOML float to be decoded. By default, this is equivalent to float(num_str). This can be used to use another datatype or parser for TOML floats (e.g. decimal.Decimal). The callable must not return a dict or a list, else a ValueError is raised.
A TOMLDecodeError will be raised on an invalid TOML document.
loads(s, /, *, parse_float=float)
Load TOML from a str object. Return a dict. Convert TOML types to Python using this conversion table <toml-to-py-table>. The parse_float argument has the same meaning as in load.
A TOMLDecodeError will be raised on an invalid TOML document.
The following exceptions are available:
TOMLDecodeError(msg, doc, pos)
Subclass of ValueError with the following additional attributes:
msg
The unformatted error message.
doc
The TOML document being parsed.
pos
The index of doc where parsing failed.
lineno
The line corresponding to pos.
colno
The column corresponding to pos.
3.14 Added the msg, doc and pos parameters. Added the msg, doc, pos, lineno and colno attributes.
3.14 Passing free-form positional arguments is deprecated.
Examples
Parsing a TOML file:
import tomllib
with open("pyproject.toml", "rb") as f:
data = tomllib.load(f)
Parsing a TOML string:
import tomllib
toml_str = """
python-version = "3.11.0"
python-implementation = "CPython"
"""
data = tomllib.loads(toml_str)
Conversion Table
| TOML | Python |
|---|---|
| TOML document | dict |
| string | str |
| integer | int |
| float | float (configurable with parse_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 |
| array of tables | list of dicts |
Limits and interoperability considerations
!tomllib places some limits on the documents it can handle, and it preserves details that other TOML parsers are allowed to ignore. When writing portable TOML files, only use features that are guaranteed or recommended by the standard.
The implementation details listed here may change in future versions of Python.
Tables/dicts
The TOML spec does not guarantee key/value pairs in TOML documents and tables to be in any specific order.
!tomllib loads dictionary entries in the order they appear in the source.
Integers
TOML recommends supporting integers in range(−2**63, 2**63).
!tomllib uses Python's limit on integer string conversion <int_max_str_digits> (4300 digits by default).
Floats
TOML recommends supporting at least IEEE 754 binary64 values, which means that numbers with more than 15 significant decimal digits are likely to be rounded.
!tomllib uses Python float by default; on many common platforms this is the recommended binary64. See sys.float_info for details.
Nesting limit
TOML 1.1.0 does not recommend a limit on how deeply arrays and tables may be nested inside one another. (A limit of 100 has been proposed for a future version of TOML.)
In !tomllib, the nesting level is mainly limited by Python's recursion limit <sys.getrecursionlimit>. Note that code that calls !tomllib may contribute to the limit.
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