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https://github.com/mk-fg/pretty-yaml

PyYAML-based module to produce a bit more pretty and readable YAML-serialized data
https://github.com/mk-fg/pretty-yaml

formatter human pretty-print python readability serialization yaml

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PyYAML-based module to produce a bit more pretty and readable YAML-serialized data

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pretty-yaml (or pyaml)

======================



PyYAML_-based python module to produce a bit more pretty and human-readable YAML-serialized data.



This module is for serialization only, see `ruamel.yaml`_ module for literate

YAML parsing (keeping track of comments, spacing, line/column numbers of values, etc).



(side-note: to dump stuff parsed by ruamel.yaml with this module, use only ``YAML(typ='safe')`` there)



It's a small module, and for projects that only need part of its functionality,

I'd recommend copy-pasting that in, instead of adding janky dependency.



.. _PyYAML: http://pyyaml.org/

.. _ruamel.yaml: https://bitbucket.org/ruamel/yaml/



.. contents::

  :backlinks: none



Repository URLs:



- https://github.com/mk-fg/pretty-yaml

- https://codeberg.org/mk-fg/pretty-yaml

- https://fraggod.net/code/git/pretty-yaml



Warning

-------



Prime goal of this module is to produce human-readable output that can be

easily diff'ed, manipulated and re-used, but maybe with occasional issues.



So please do not rely on the thing to produce output that can always be

deserialized exactly to what was exported, at least - use PyYAML directly

for that (but maybe with options from the next section).



Output also isn't guaranteed to be stable between module versions,

as new representation tweaks get added occasionally, but these can usually

be disabled via module parameters, to get output stability over improvements.



What this module does and why

-----------------------------



YAML is generally nice and easy format to read *if* it was written by humans.



PyYAML can a do fairly decent job of making stuff readable, and the best

combination of parameters for such output that I've seen so far is probably this one::



  >>> m = [123, 45.67, {1: None, 2: False}, 'some text']

  >>> data = dict(a='asldnsa\nasldpáknsa\n', b='whatever text', ma=m, mb=m)

  >>> yaml.safe_dump( data, sys.stdout,

    width=100, allow_unicode=True, default_flow_style=False )

  a: 'asldnsa



    asldpáknsa



    '

  b: whatever text

  ma: &id001

  - 123

  - 45.67

  - 1: null

    2: false

  - some text

  mb: *id001



pyaml (this module) tries to improve on that a bit, with the following tweaks:



* Most human-friendly representation options in PyYAML (that I know of)

  are used as defaults - unicode, flow-style, width=100 (old default is 80).



* Dump "null" values as empty values, if possible, which have the same meaning

  but reduce visual clutter and are easier to edit.



* Dicts, sets, OrderedDicts, defaultdicts, namedtuples, enums, dataclasses, etc

  are represented as their safe YAML-compatible base (like int, list or mapping),

  with mappings key-sorted by default for more diff-friendly output.



* Use shorter and simpler yes/no for booleans.



* List items get indented, as they should be.



* Attempt is made to pick more readable string representation styles, depending

  on the value, e.g.::



    >>> yaml.safe_dump(cert, sys.stdout)

    cert: '-----BEGIN CERTIFICATE-----



      MIIH3jCCBcagAwIBAgIJAJi7AjQ4Z87OMA0GCSqGSIb3DQEBCwUAMIHBMRcwFQYD



      VQQKFA52YWxlcm9uLm5vX2lzcDEeMBwGA1UECxMVQ2VydGlmaWNhdGUgQXV0aG9y

    ...



    >>> pyaml.p(cert):

    cert: |

      -----BEGIN CERTIFICATE-----

      MIIH3jCCBcagAwIBAgIJAJi7AjQ4Z87OMA0GCSqGSIb3DQEBCwUAMIHBMRcwFQYD

      VQQKFA52YWxlcm9uLm5vX2lzcDEeMBwGA1UECxMVQ2VydGlmaWNhdGUgQXV0aG9y

    ...



* "force_embed" option (default=yes) to avoid having &id stuff scattered all

  over the output. Might be more useful to disable it in some specific cases though.



* "&idXYZ" anchors, when needed, get labels from the keys they get attached to,

  not just meaningless enumerators, e.g. "&users_-_admin" instead.



* "string_val_style" option to only apply to strings that are values, not keys,

  i.e::



    >>> pyaml.p(data, string_val_style='"')

    key: "value\nasldpáknsa\n"

    >>> yaml.safe_dump(data, sys.stdout, allow_unicode=True, default_style='"')

    "key": "value\nasldpáknsa\n"



* Add vertical spacing (empty lines) between keys on different depths,

  to separate long YAML sections in the output visually, make it more seekable.



* Discard end-of-document "..." indicators for simple values.



Result for the (rather meaningless) example above::



  >>> pyaml.p(data, force_embed=False, vspacing=dict(split_lines=10))



  a: |

    asldnsa

    asldpáknsa



  b: whatever text



  ma: &ma

    - 123

    - 45.67

    - 1:

      2: no

    - some text



  mb: *ma



(force_embed=False enabled deduplication with ``&ma`` anchor,

vspacing is adjusted to split even this tiny output)



----------



Extended example::



  >>> pyaml.dump(data, vspacing=dict(split_lines=10))



  destination:



    encoding:

      xz:

        enabled: yes

        min_size: 5120

        options:

        path_filter:

          - \.(gz|bz2|t[gb]z2?|xz|lzma|7z|zip|rar)$

          - \.(rpm|deb|iso)$

          - \.(jpe?g|gif|png|mov|avi|ogg|mkv|webm|mp[34g]|flv|flac|ape|pdf|djvu)$

          - \.(sqlite3?|fossil|fsl)$

          - \.git/objects/[0-9a-f]+/[0-9a-f]+$



    result:

      append_to_file:

      append_to_lafs_dir:

      print_to_stdout: yes



    url: http://localhost:3456/uri



  filter:

    - /(CVS|RCS|SCCS|_darcs|\{arch\})/$

    - /\.(git|hg|bzr|svn|cvs)(/|ignore|attributes|tags)?$

    - /=(RELEASE-ID|meta-update|update)$



  http:

    ca_certs_files: /etc/ssl/certs/ca-certificates.crt

    debug_requests: no

    request_pool_options:

      cachedConnectionTimeout: 600

      maxPersistentPerHost: 10

      retryAutomatically: yes



  logging:



    formatters:

      basic:

        datefmt: '%Y-%m-%d %H:%M:%S'

        format: '%(asctime)s :: %(name)s :: %(levelname)s: %(message)s'



    handlers:

      console:

        class: logging.StreamHandler

        formatter: basic

        level: custom

        stream: ext://sys.stderr



    loggers:

      twisted:

        handlers:

          - console

        level: 0



    root:

      handlers:

        - console

      level: custom



Note that unless there are many moderately wide and deep trees of data,

which are expected to be read and edited by people, it might be preferrable

to directly use PyYAML regardless, as it won't introduce another

(rather pointless in that case) dependency and a point of failure.



Features and Tricks

-------------------



* Pretty-print any yaml or json (yaml subset) file from the shell::



    % python -m pyaml /path/to/some/file.yaml

    % pyaml < myfile.yml

    % curl -s https://www.githubstatus.com/api/v2/summary.json | pyaml



  ``pipx install pyaml`` can be a good way to only install "pyaml" command-line script.



* Process and replace json/yaml file in-place::



    % python -m pyaml -r mydata.yml



* Easier "debug printf" for more complex data (all funcs below are aliases to same thing)::



    pyaml.p(stuff)

    pyaml.pprint(my_data)

    pyaml.pprint('----- HOW DOES THAT BREAKS!?!?', input_data, some_var, more_stuff)

    pyaml.print(data, file=sys.stderr) # needs "from __future__ import print_function"



* Force all string values to a certain style (see info on these in `PyYAML docs`_)::



    pyaml.dump(many_weird_strings, string_val_style='|')

    pyaml.dump(multiline_words, string_val_style='>')

    pyaml.dump(no_want_quotes, string_val_style='plain')



  Using ``pyaml.add_representer()`` (note \*p\*yaml) as suggested in

  `this SO thread`_ (or `github-issue-7`_) should also work.



  See also this `amazing reply to StackOverflow#3790454`_ for everything about

  the many different string styles in YAML.



* Control indent and width of the results::



    pyaml.dump(wide_and_deep, indent=4, width=120)



  These are actually keywords for PyYAML Emitter (passed to it from Dumper),

  see more info on these in `PyYAML docs`_.



* Dump multiple yaml documents into a file: ``pyaml.dump_all([data1, data2, data3], dst_file)``



  explicit_start=True is implied, unless overidden by explicit_start=False.



* Control thresholds for vertical spacing of values (0 = always space stuff out),

  and clump all oneliner ones at the top::



    >>> pyaml.dump( data,

      sort_dicts=pyaml.PYAMLSort.oneline_group,

      vspacing=dict(split_lines=0, split_count=0) )



    chart:

      axisCenteredZero: no

      axisColorMode: text

      axisLabel: ''

      axisPlacement: auto

      barAlignment: 0

      drawStyle: line

      ...



      hideFrom:

        legend: no

        tooltip: no

        viz: no



      scaleDistribution:

        type: linear



      stacking:

        group: A

        mode: none



  Or same thing with cli tool ``-v/--vspacing`` option: ``pyaml -v 0/0g mydata.yaml``



.. _PyYAML docs: http://pyyaml.org/wiki/PyYAMLDocumentation#Scalars

.. _this SO thread: http://stackoverflow.com/a/7445560

.. _github-issue-7: https://github.com/mk-fg/pretty-yaml/issues/7

.. _amazing reply to StackOverflow#3790454:

  https://stackoverflow.com/questions/3790454/how-do-i-break-a-string-in-yaml-over-multiple-lines/21699210#21699210



Installation

------------



It's a regular Python 3.8+ module/package, published on PyPI (as pyaml_).



Module uses PyYAML_ for processing of the actual YAML files

and should pull it in as a dependency.



Dependency on unidecode_ module is optional and only be used with

force_embed=False keyword (defaults to True), and same-id objects

or recursion within serialized data - i.e. only when generating

&some_key_id anchors is actually needed.

If module is unavailable at runtime, anchor ids might be less like their

keys and maybe not as nice.



Using pip_ is how you generally install it, usually coupled with venv_ usage

(which will also provide "pip" tool itself)::



  % pip install pyaml



Current-git version can be installed like this::



  % pip install git+https://github.com/mk-fg/pretty-yaml



pip will default to installing into currently-active venv, then user's home

directory (under ``~/.local/lib/python...``), and maybe system-wide when running

as root (only useful in specialized environments like docker containers).



There are many other python packaging tools - pipenv_, poetry_, pdm_, etc -

use whatever is most suitable for specific project/environment.

pipx_ can be used to install command-line script without a module.



More general info on python packaging can be found at `packaging.python.org`_.



When changing code, unit tests can be run with ``python -m unittest``

from the local repository checkout.



.. _pyaml: https://pypi.org/project/pyaml/

.. _unidecode: https://pypi.python.org/pypi/Unidecode

.. _pip: https://pip.pypa.io/en/stable/

.. _venv: https://docs.python.org/3/library/venv.html

.. _poetry: https://python-poetry.org/

.. _pipenv: https://pipenv.pypa.io/

.. _pdm: https://pdm.fming.dev/

.. _pipx: https://pypa.github.io/pipx/

.. _packaging.python.org: https://packaging.python.org/installing/