How can I control what scalar form PyYAML uses for my data?

Falling in love with @lbt’s approach, I got this code:

import yaml

def str_presenter(dumper, data):
  if len(data.splitlines()) > 1:  # check for multiline string
    return dumper.represent_scalar(',2002:str', data, style="|")
  return dumper.represent_scalar(',2002:str', data)

yaml.add_representer(str, str_presenter)

# to use with safe_dump:
yaml.representer.SafeRepresenter.add_representer(str, str_presenter)

It makes every multiline string be a block literal.

I was trying to avoid the monkey patching part.
Full credit to @lbt and @J.F.Sebastian.

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