Any yaml libraries in Python that support dumping of long strings as block literals or folded blocks?

Question

I'd like to be able to dump a dictionary containing long strings that I'd like to have in the block style for readability. For example:

foo: |
  this is a
  block literal
bar: >
  this is a
  folded block

PyYAML supports the loading of documents with this style but I can't seem to find a way to dump documents this way. Am I missing something?

Answer 1

import yaml

class folded_unicode(unicode): pass
class literal_unicode(unicode): pass

def folded_unicode_representer(dumper, data):
    return dumper.represent_scalar(u'tag:yaml.org,2002:str', data, style='>')
def literal_unicode_representer(dumper, data):
    return dumper.represent_scalar(u'tag:yaml.org,2002:str', data, style='|')

yaml.add_representer(folded_unicode, folded_unicode_representer)
yaml.add_representer(literal_unicode, literal_unicode_representer)

data = {
    'literal':literal_unicode(
        u'by hjw              ___\n'
         '   __              /.-.\\\n'
         '  /  )_____________\\\\  Y\n'
         ' /_ /=== == === === =\\ _\\_\n'
         '( /)=== == === === == Y   \\\n'
         ' `-------------------(  o  )\n'
         '                      \\___/\n'),
    'folded': folded_unicode(
        u'It removes all ordinary curses from all equipped items. '
        'Heavy or permanent curses are unaffected.\n')}

print yaml.dump(data)

The result:

folded: >
  It removes all ordinary curses from all equipped items. Heavy or permanent curses
  are unaffected.
literal: |
  by hjw              ___
     __              /.-.\
    /  )_____________\\  Y
   /_ /=== == === === =\ _\_
  ( /)=== == === === == Y   \
   `-------------------(  o  )
                        \___/

For completeness, one should also have str implementations, but I'm going to be lazy :-)