keep source unformatted while YAML dump

Question

My YAML file looks like below:

info_block:
  enable: null
  start: "12:00"
  server_type: linux

I have loaded and dumped using ruamel.yaml.dump

But, the output is getting formatted like below: (like null replaced to empty, double quotes gets removed from the start value)

info_block:
  enable:
  start: 12:00
  server_type: linux

How can I retain my source here

I know there is something like this to retain the null but I want my complete source unformatted.

score 0 · Accepted Answer · answered Jun 10 '20 at 18:36

If you want to retain your source, you're best bet is to keep track of whether something changes and not over write the source when not changes, as in your example.

ruamel.yaml will always normalize output and if that is not what you want, your only hope is to do exact string substitutions on the file, potentially using the line information on the loaded data. I recommend against doing that, and if you're retaining is for minizing diffs you should just byte the bullet once, like what you would do when using some source formatter.

However if you work with YAML 1.1 only parsers although that version was replaced more than 10 years ago, I can see that 12:00 instead of "12:00" can be a problem as those kind of strings are interpreted as sexagesimals.

In ruamel.yaml, you can either set the output to be YAML 1.1, and then 12:00 will be quoted, but you'll get a document header stating that it is conform to the outdated version.

The other thing you can do is preserve any quotes using the .preserve_quotes attribute:

import sys
import ruamel.yaml

yaml_str = """\
info_block:
  enable: null
  start: "12:00"
  server_type: linux
"""


def my_represent_none(self, data):
    return self.represent_scalar(u'tag:yaml.org,2002:null', u'null')

yaml = ruamel.yaml.YAML()
yaml.representer.add_representer(type(None), my_represent_none)

yaml.indent(mapping=2, sequence=2, offset=0)
yaml.preserve_quotes = True

data = yaml.load(yaml_str)

yaml.dump(data, sys.stdout)

which gives a complete retained version if combined with the alternative representer for the null node:

info_block:
  enable: null
  start: "12:00"
  server_type: linux

keep source unformatted while YAML dump

1 Answers1