version: 0.2
text: md
pdf: false
--- |
# Differences with PyYAML

::: parsed-literal

*If I have seen further, it is by standing on the shoulders of giants*.

:   Isaac Newton (1676)
:::

`ruamel.yaml` is a derivative of Kirill Simonov\'s [PyYAML
3.11](https://bitbucket.org/xi/pyyaml) and would not exist without that
excellent base to start from.

The following a summary of the major differences with PyYAML 3.11

## Defaulting to YAML 1.2 support

PyYAML supports the [YAML 1.1]() standard, `ruamel.yaml` supports [YAML
1.2]() as released in 2009.

-   YAML 1.2 dropped support for several features unquoted `Yes`, `No`,
    `On`, `Off`
-   YAML 1.2 no longer accepts strings that start with a `0` and solely
    consist of number characters as octal, you need to specify such
    strings with `0o[0-7]+` (zero + lower-case o for octal + one or more
    octal characters).
-   YAML 1.2 no longer supports
    [sexagesimals](https://en.wikipedia.org/wiki/Sexagesimal), so the
    string scalar `12:34:56` doesn\'t need quoting.
-   `\/` escape for JSON compatibility
-   correct parsing of floating point scalars with exponentials

unless the YAML document is loaded with an explicit `version==1.1` or
the document starts with:

    % YAML 1.1

, `ruamel.yaml` will load the document as version 1.2.

## PY2/PY3 reintegration

`ruamel.yaml` re-integrates the Python 2 and 3 sources, running on
Python 2.7 (CPython, PyPy), 3.3, 3.4, 3.5 and 3.6 (support for 2.6 has
been dropped mid 2016). It is more easy to extend and maintain as only a
miniscule part of the code is Python version specific.

## Fixes

-   `ruamel.yaml` follows the `indent` keyword argument on scalars when
    dumping.
-   `ruamel.yaml` allows `:` in plain scalars, as long as these are not
    followed by a space (as per the specification)

## Testing

`ruamel.yaml` is tested using [tox]() and [py.test](). In addition to
new tests, the original PyYAML test framework is called from within
`tox` runs.

Before versions are pushed to PyPI, `tox` is invoked, and has to pass,
on all supported Python versions, on PyPI as well as flake8/pep8

## API

Starting with 0.15 the API for using `ruamel.yaml` has diverged allowing
easier addition of new features.
--- !inc-raw
- links.rydinc