How can i output empty value in yythl python file
If you download YAML SRC
allow:
in Python you get None
assigned to a key allow
, this is the correct behavior.
If you are using ruamel.yaml ( the author of which I am) and RoundTripDumper
, None
being written as you want (which is IMO the most readable, though not explicit):
import ruamel.yaml
print ruamel.yaml.dump(dict(allow=None), Dumper=ruamel.yaml.RoundTripDumper)
I will give you:
allow:
You can also correctly back and forth this:
import ruamel.yaml
yaml_src = """
allow:
key2: Hello # some test
"""
data = ruamel.yaml.load(yaml_src, ruamel.yaml.RoundTripLoader)
print('#### 1')
print(data['allow'])
print('#### 2')
print(ruamel.yaml.dump(data, Dumper=ruamel.yaml.RoundTripDumper))
print('#### 3')
print(type(data))
get as output:
#### 1
None
#### 2
allow:
key2: Hello # some test
#### 3
<class 'ruamel.yaml.comments.CommentedMap'>
The above data
are a subclass of orderdict, which is needed to keep track of the style of the input stream, handle comments attached to lines, order of keys, etc.
Such a subclass can be created on the fly, but it is usually easier to start with some readable and well-formatted YAML code (possibly already saved to disk) and then update / expand the values.
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from yaml import SafeDumper
import yaml
data = {'deny': None, 'allow': None}
SafeDumper.add_representer(
type(None),
lambda dumper, value: dumper.represent_scalar(u'tag:yaml.org,2002:null', '')
)
with open('./yadayada.yaml', 'w') as output:
yaml.safe_dump(data, output, default_flow_style=False)
There is a way to do this inline in python yaml itself. The above code will create a file containing:
allow:
deny:
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Using replace, it looks simple:
import yaml
fname = 'test.yaml'
with open(fname, "w") as f:
yaml_str = yaml.safe_dump({'allow':'', 'deny': ''},
default_flow_style=False,
width=50,
indent=4).replace(r"''", '')
f.write(yaml_str)
Is there a reason you want to avoid replace
?
There is a disadvantage that reloading the yaml file does not reproduce your input:
>>> print yaml.safe_load(open(fname))
{'deny': None, 'allow': None}
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