在Pyyaml中,如何用块样式表示空字符串和列表？

Question

我已经添加了折叠字符串的表示符,如Python中的任何yaml库中提到的文字字符串,支持将长字符串转储为块文字或折叠块？.我还添加了representer来在转储的yaml内容中以块样式打印列表.

但问题是当字符串为空时,即""或列表为空时,它们在转储的YAML内容中以非块样式出现.

如何强制pyyaml转储器输出带有">"或"|"的空字符串 生成的YAML内容中的块样式中的flow_style = False的样式和空列表？

Answer 1

经过一些研究,我可以使用Pyyaml在YAML文件中将空字符串转储为块文字(样式在'|>'中).我的工作部分基于Python中的任何yaml库,它支持将长字符串转储为块文字或折叠块？.

import yaml
from yaml.emitter import Emitter, ScalarAnalysis

class MyEmitter(Emitter):  
    def analyze_scalar(self, scalar):   
        # Empty scalar is a special case.
        # By default, pyyaml sets allow_block=False
        # I override this to set allow_block=True
        if not scalar:         
            return ScalarAnalysis(scalar=scalar, empty=True, multiline=False,
                allow_flow_plain=False, allow_block_plain=True,
                allow_single_quoted=True, allow_double_quoted=True,
                allow_block=True)   
        return super(MyEmitter, self).analyze_scalar(scalar)

# And I subclass MyDumper from MyEmitter and yaml.Dumper        
class MyDumper(yaml.Dumper, MyEmitter):
    pass
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)

# I test it now
d = {'foo': {'folded': folded_unicode(''), 'literal': literal_unicode('')}}
print yaml.dump(d, Dumper=MyDumper)

输出:

foo:
  folded: >
  literal: |

但是,我无法找到以块样式转储空列表的方法.为此,我试图弄乱yaml/emitter.py并意识到我需要一个非空列表以块样式转储它.

无论如何,这种努力并没有白费,而是非常令人兴奋:)我希望有人可能会觉得这很有用或者可能有分享的东西.