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How to add curly brackets and hyphen to a yaml in python

I have a python script that generates yaml files with pyyaml and I need something like this in the output:

key: {{- something }}

When I try to add this in my dictionary object

{ "key": "{{- something }}" }

the output will be this:

key: '{{- something }}'

Is there a workaround where I can put braces into the dictionary value? Thanks!

I tried string formatting or putting the {{- something }} into a variable but it always prints it with the '' marks.

Solution

  • This is not possible with PyYAML or any conforming YAML implementation.

    This:

    key: {{- something }}

    is invalid YAML because { starts a flow mapping, while - starts a block sequence item. While you can nest flow mappings, you cannot put a block sequence item into a flow mapping.

    You cannot use a YAML implementation to create invalid YAML, as the point of a YAML implementation is to always output valid YAML.

    You are probably not actually generating YAML files, but Jinja templates that compile to YAML files (guessing from the fact that {{- something}} is a typical Jinja construct). A YAML implementation cannot help you generate files that need to be processed by a templating engine to become valid YAML files.

    There are some workarounds. For example, you could output

    key: _something_

    and then post-process the output to replace _something_ with {{- something}}. I chose _something_ because that's a format PyYAML does not quote by default.