Pyyaml And Using Quotes For Strings Only

I have the following YAML file: --- my_vars: my_env: 'dev' my_count: 3 When I read it with PyYAML and dump it again, I get the following output: --- my_vars: my_env: dev m

Solution 1:

I suggest you update to using YAML 1.2 (released in 2009) with the backwards compatible ruamel.yaml package instead of using PyYAML which implements most of YAML 1.1 (2005). (Disclaimer: I am the author of that package).

Then you just specify preserve_quotes=True when loading for round-tripping the YAML file:

import sys
import ruamel.yaml

yaml_str = """\
---
my_vars:
  my_env: "dev"    # keep "dev" quoted
  my_count: 3
"""

data = ruamel.yaml.round_trip_load(yaml_str, preserve_quotes=True)
ruamel.yaml.round_trip_dump(data, sys.stdout, explicit_start=True)

which outputs (including the preserved comment):

---my_vars:my_env:"dev"# keep "dev" quotedmy_count:3

After loading the string scalars will be a subclass of string, to be able to accommodate the quoting info, but will work like a normal string for all other purposes. If you want to replace such a string though (dev to fgw) you have to cast the string to this subclass ( DoubleQuotedScalarString from ruamel.yaml.scalarstring).

When round-tripping ruamel.yaml by default preserves the order (by insertion) of the keys.

Solution 2:

Right, so borrowing heavily from this answer, you can do something like this:

import yaml

# define a custom representer for stringsdefquoted_presenter(dumper, data):
    return dumper.represent_scalar('tag:yaml.org,2002:str', data, style='"')

yaml.add_representer(str, quoted_presenter)


env_file = 'input.txt'withopen(env_file) as f:
    env_dict = yaml.load(f)
    print yaml.dump(env_dict, default_flow_style=False)

However, this just overloads it on all strings types in the dictionary so it'll quote the keys as well, not just the values.

It prints:

"my_vars":"my_count":3"my_env":"dev"

Is this what you want? Not sure what you mean by variable names, do you mean the keys?

Solution 3:

you can use the following method to retain your double quoted scalar object in yaml:

Taking your yaml example:

---my_vars:my_env:"dev"my_count:3

Loading it into an env_dict (dictionary):

myyaml = '''
---
my_vars:
  my_env: "dev"
  my_count: 3
'''

env_dict = yaml.load(myyaml, yaml.FullLoader) # loading yamlprint(env_dict)
{'my_vars': {'my_env': 'dev', 'my_count': 3}}

# Define a quoted class, which uses style = '"' and add representer to yamlclassquoted(str):
    passdefquoted_presenter(dumper, data):
    return dumper.represent_scalar('tag:yaml.org,2002:str', data, style='"')
yaml.add_representer(quoted, quoted_presenter)


# Now, we update the dictionary env_dict as follows for the "dev" # value which needs to be a double quoted scalar

env_dict['my_vars'].update(my_env = quoted("dev")) # this makes "dev"# a double quoted scalar# Now, we dump the yaml as before

yaml.dump(env_dict, sys.stdout, indent=4, default_flow_style=False, explicit_start=True)

# which outputs

---
my_vars:
    my_count: 3
    my_env: "dev"

These links helped me to arrive at this answer : Any yaml libraries in Python that support dumping of long strings as block literals or folded blocks?

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

Also, this one is a great article to read on To Quote or not to Quote?

Hope, this helps!