1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
ruamel.yaml
===========
``ruamel.yaml`` is a YAML package for Python. It is a derivative
of Kirill Simonov's `PyYAML 3.11 <https://bitbucket.org/xi/pyyaml>`_
which supports YAML1.1
Major differences with PyYAML 3.11:
- intergrated Python 2 and 3 sources, running on Python 2.6, 2.7, 3.3 and 3.4.
- round trip mode that **includes comments** (block mode, key ordering kept)
- support for simple lists as mapping keys by transformation to tuples
- ``!!omap`` generates ordereddict (C) on Python 2, collections.OrderedDict
on Python 3, and ``!!omap`` is generated for these types.
- some YAML 1.2 enhancements (``0o`` octal prefix, ``\/`` escape)
- pep8 compliance
- tox and py.test based testing
- Tests whether the C yaml library is installed as well as the header
files. That library doesn't generate CommentTokens, so it cannot be used to
do round trip editing on comments. It can be used for speeded up normal
processing (so you don't need to install ``ruamel.yaml`` and ``PyYaml``).
See the section *Optional requirements*.
- Basic support for multiline strings with preserved newlines and
chomping ( '``|``', '``|+``', '``|-``' ). As this subclasses the string type
the information is lost on reassignment. (This might be changed
in the future so that the preservation/folding/chomping is part of the
parent container, like comments).
- RoundTrip preservation of flow style sequences ( 'a: b, c, d') (based
on request and test by Anthony Sottile)
Round trip including comments
=============================
The major motivation for this fork is the round-trip capability for
comments. The integration of the sources was just an initial step to
make this easier.
Config file formats
-------------------
There are only a few configuration file formats that are human
readable and editable: JSON, INI/ConfigParser, YAML (XML is to verbose
to be readable).
Unfortunately `JSON <http://www.json.org/>`_ doesn't support comments,
and although there are some solutions with pre-processed filtering of
comments, there are no libraries that support round trip updating of
such commented files.
INI files support comments, and the excellent `ConfigObj
<http://www.voidspace.org.uk/python/configobj.html>`_ library by Foord
and Larosa even supports round trip editing with comment preservation,
nesting of sections and limited lists (within a value). Retrieval of
particular value format is explicit (and extensible).
YAML has basic mapping and sequence structures as well support for
ordered mappings and sets. It supports scalars are of various types
including dates and datetimes (missing in JSON) as a list of
YAML has comments, but these are normally thrown away.
Block structured YAML is a clean and very human readable
format. By extending the Python YAML parser to support round trip
preservation of comments, it makes YAML a very good choice for
configuration files that are human readable and editable while at
the same time interpretable and modifiable by a program.
Extending
---------
There are normally 6 files involved when extending the roundtrip
capabilities: the reader, parser, composer and constructor to go from YAML to
Python and the resolver, representer, serializer and emitter to go the other
way.
Extending involves keeping extra data around for the next process step,
eventuallly resulting in a different Python object (subclass or alternative),
that should behave like the original, but on the way from Python to YAML
generates the original (or at least something much closer).
Examples
========
Basic round trip of parsing YAML to Python objects, modifying
and generating YAML::
from __future__ import print_function
import ruamel.yaml
inp = """\
# example
name:
# details
family: Smith # very common
given: Alice # one of the siblings
"""
code = ruamel.yaml.load(inp, ruamel.yaml.RoundTripLoader)
code['name']['given'] = 'Bob'
print(ruamel.yaml.dump(code, Dumper= ruamel.yaml.RoundTripDumper), end='')
.. example code small.py
Resulting in ::
# example
name:
# details
family: Smith # very common
given: Bob # one of the siblings
.. example output small.py
Optional requirements
=====================
If you have the C yaml library and headers installed, as well as
the header files for your Python executables then you can use the
non-roundtrip but faster C loader en emitter.
On Debian systems you should use::
sudo apt-get install libyaml-dev python-dev python3-dev
you can leave out ``python3-dev`` if you don't use python3
For CentOS (7) based systems you should do::
sudo yum install libyaml-devel python-devel
Testing
=======
Testing is done using the `tox <https://pypi.python.org/pypi/tox>`_, which
uses `virtualenv <https://pypi.python.org/pypi/virtualenv>`_ and
`pytest <http://pytest.org/latest/>`_.
yaml utlity
===========
A utility name ``yaml`` is included and allows for basic operations on files:
- ``yaml round-trip <file_name>`` for basic roundtrip testing of YAML
files
- ``yaml json <file_name>`` for conversion of JSON file(s) to a single
YAML block style document
- ``yaml ini <file_name>`` for conversion of an INI/config file (ConfigObj
comment and nested sections supported) to a YAML block style document.
This requires ``configobj`` to be installed (``pip install configobj``)
- ``yaml html <file_name>`` for conversion of the basic structure in a YAML
file to a a table in an HTML file. The YAML file::
title:
- fruit
- legume
local:
- apple
- sprouts
import:
- orange
- broccoli
is converted into the table:
====== ====== ========
title fruit legume
local apple sprouts
import orange broccoli
====== ====== ========
See ``yaml --help`` for more information on the availble commands
|
