PyYAML dumping a long string over multiple lines

Question

pyYAML is dumping a long string over multiple lines. I want the output to be like this -

include:
  - interface Vlan6[\s]+vrrpv3 1 address-family ipv4[\s]+address 5.2.1.1 primary[\s]+interface Vlan7[\s]+vrrpv3 1 address-family ipv4[\s]+address 5.2.1.2

However the dump output in the file is coming like this -

include:
  - interface Vlan6[\s]+vrrpv3 1 address-family ipv4[\s]+address 5.2.1.1
    primary[\s]+interface Vlan7[\s]+vrrpv3 1 address-family ipv4[\s]+address
    5.2.1.2

Even came across a link about resolving this using SafeDumper, but I am using another custom dumper to dump into a file for a different use case (fixing indentation). Here is the code -

# MyDumper Class: To correct the indentation of list items
# https://stackoverflow.com/questions/25108581/python-yaml-dump-bad-indentation
class MyDumper(yaml.Dumper):

    def increase_indent(self, flow=False, indentless=False):
        return super(MyDumper, self).increase_indent(flow, False)


# Use str for python3 and unicode for lower versions
# https://stackoverflow.com/questions/6432605/any-yaml-libraries-in-python-that-support-dumping-of-long-strings-as-block-liter   
class literal_unicode(str): pass

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

yaml.add_representer(literal_unicode, literal_unicode_representer)


# save_verify_target -> configure -> commands
key1 = 'interface Vlan6\nvrrpv3 1 address-family ipv4\naddress 5.2.1.1 primary\ninterface vlan 7\nvrrpv3 1 address-family ipv4\naddress 5.2.1.2\n'
# save_verify_target -> execute -> commands
key2 = 'show file vrrp.cfg'

verify_target_str = 'interface Vlan6[\s]+vrrpv3 1 address-family ipv4[\s]+address 5.2.1.1 primary[\s]+interface Vlan7[\s]+vrrpv3 1 address-family ipv4[\s]+address 5.2.1.2'

dict_file = {
    'extends': 'common_trigger.yaml',
    'setup_device': {
        'description': 'Setup device',
        'source': {
            'pkg': 'libs.sdk'
        },
        'groups': ['all', 'custom']
    },
    'Test01': {
        'description': 'ID:TC01',
        'source': {
            'pkg': 'libs.sdk'
        },
        'groups': ['all', 'custom'],
        'test_sections': [
            '%{ triggers.pre_config }',
            {'save_verify_target': [
                {'configure': {
                    'custom_start_step_message': 'Save target config to a file',
                    'device': 'uut1',
                    'command': literal_unicode(key1)
                }},
                {'execute': {
                    'custom_start_step_message': 'Verify the target file contents',
                    'device': 'uut1',
                    'command': literal_unicode(key2),
                    'include': [verify_target_str]
                }}
            ]}
        ]
    }
}

with open(r'check.yaml', 'w') as file:
    documents = yaml.dump(dict_file, file, sort_keys=False, Dumper=MyDumper, default_flow_style=False)

Here 'verify_target_str' which is a value for key 'include' is a very long string and I want it to come in one single line in the final YAML file i.e. check.yaml.

Can someone please help?

score 2 · Accepted Answer · answered Jun 25 '23 at 12:40

PyYAML's dump has an argument width which defaults (IIRC) to 78, and that is where long lines get wrapped. Just pass it a large enough value that wrapping is no longer necessary.

Of course your wish to have this on one line is irrelevant wrt proper YAML parsers. Those, and even PyYAML itself, will load the wrapped scalar to the original Python string.

PyYAML dumping a long string over multiple lines

1 Answers1