GitHub - crdoconnor/strictyaml: Type-safe YAML parser and validator.
source link: https://github.com/crdoconnor/strictyaml
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README.rst
StrictYAML
StrictYAML is a type-safe YAML parser that parses a restricted subset of the YAML specificaton.
Priorities:
- Beautiful API
- Refusing to parse the ugly, hard to read and insecure features of YAML.
- Strict validation of markup and straightforward type casting.
- Clear, readable exceptions with code snippets and line numbers.
- Acting as a near-drop in replacement for pyyaml, ruamel.yaml or poyo.
- Ability to read in YAML, make changes and write it out again with comments preserved.
- Not speed, currently.
Simple example:
# All about the character name: Ford Prefect age: 42 possessions: - Towel
from strictyaml import load, Map, Str, Int, Seq, YAMLError
Default parse result:
>>> load(yaml_snippet) YAML(OrderedDict([('name', 'Ford Prefect'), ('age', '42'), ('possessions', ['Towel'])]))
All data is string, list or OrderedDict:
>>> load(yaml_snippet).data OrderedDict([('name', 'Ford Prefect'), ('age', '42'), ('possessions', ['Towel'])])
Quickstart with schema:
from strictyaml import load, Map, Str, Int, Seq, YAMLError schema = Map({"name": Str(), "age": Int(), "possessions": Seq(Str())})
42 is now parsed as an integer:
>>> person = load(yaml_snippet, schema) >>> person.data OrderedDict([('name', 'Ford Prefect'), ('age', 42), ('possessions', ['Towel'])])
A YAMLError will be raised if there are syntactic problems, violations of your schema or use of disallowed YAML features:
# All about the character name: Ford Prefect age: 42
For example, a schema violation:
try: person = load(yaml_snippet, schema) except YAMLError as error: print(error)
while parsing a mapping in "<unicode string>", line 1, column 1: # All about the character ^ (line: 1) required key(s) 'possessions' not found in "<unicode string>", line 3, column 1: age: '42' ^ (line: 3)
If parsed correctly:
from strictyaml import load, Map, Str, Int, Seq, YAMLError schema = Map({"name": Str(), "age": Int(), "possessions": Seq(Str())})
You can modify values and write out the YAML with comments preserved:
person = load(yaml_snippet, schema) person['age'] = 43 print(person.as_yaml())
# All about the character name: Ford Prefect age: 43 possessions: - Towel
As well as look up line numbers:
>>> person = load(yaml_snippet, schema) >>> person['possessions'][0].start_line 5
Install
$ pip install strictyaml
Why StrictYAML?
There are a number of formats and approaches that can achieve more or less the same purpose as StrictYAML. I've tried to make it the best one. Below is a series of documented justifications:
- Why not JSON for simple configuration files?
- Why not use HJSON?
- Why not use TOML?
- Why not use the YAML 2.0 standard? - we don't need a new standard!
- Why not use kwalify with standard YAML to validate my YAML?
- Why not use python's schema library for validation?
- Why not HOCON?
- Why not JSON5?
- Why not use XML for configuration or DSLs?
- Why shouldn't I just use python code for configuration?
- Why not use INI files?
- Why not use SDLang?
- Why not use JSON Schema for validation?
Using StrictYAML
- compound
- Validating optional keys in mappings (Map)
- Using a YAML object of a parsed mapping
- Sequences of unique items (UniqueSeq)
- Mappings with defined keys (Map)
- Mappings with arbitrary key names (MapPattern)
- Fixed length sequences (FixedSeq)
- Sequence/list validator (Seq)
- Mapping with defined keys and a custom key validator (Map)
- howto
- Revalidate an already validated document
- Merge YAML documents
- Parsing YAML without a schema
- Labeling exceptions
- Build a YAML document from scratch in code
- Reading in YAML, editing it and writing it back out
- Get line numbers of YAML elements
- Either/or schema validation of two equally valid different kinds of YAML
- scalar
- Validating strings with regexes (Regex)
- Integers (Int)
- Empty key validation
- Floating point numbers (Float)
- Decimal numbers (Decimal)
- Enumerated scalars (Enum)
- Parsing strings (Str)
- Boolean (Bool)
- Email and URL validators
- Datetimes (Datetime)
- Parsing comma separated items (CommaSeparated)
- restrictions
- Disallowed YAML
- Duplicate keys
Design justifications
There are some design decisions in StrictYAML which are controversial and/or not obvious. Those are documented here:
- What is wrong with explicit tags?
- What is wrong with explicit syntax typing in a readable configuration language?
- What is wrong with implicit typing?
- What is wrong with flow style YAML?
- Why does StrictYAML only parse from strings and not files?
- What is wrong with duplicate keys?
- Why does StrictYAML not parse direct representations of python objects?
- What is wrong with node anchors and references?
- Why does StrictYAML make you define a schema in python - a turing complete language?
Breaking changes
0.5: Data is now parsed by default as a YAML object instead of directly to dict/list. To get dict/list and ordinary values as before, get yaml_object.data.
Contributors
- @gvx
- @AlexandreDecan
- @lots0logs
- @tobbez
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