Metaparser module

metaparser - the infrastructure class to define and regulate parser object execution.

class genie.metaparser._metaparser.classproperty(fget=None, fset=None, fdel=None, doc=None)

Bases: property

decorator class to access the class property

class genie.metaparser._metaparser.MetaParser(device, *, context='cli', **kwargs)

Bases: object

Base parser class for all Genie parser classes

All parser classes will inherit from MetaParser class, for example: ShowVersion, etc.

Parameters

• device (Device) – device which the parser function will be applied to

• context (str) – a keyword only arg acting as a selector for user to choose which parsing mechanism will be used to current parsing task. choices of: ‘cl’, ‘xml’, ‘yang’, default is ‘cli’.

• kwargs (dict) – gives the user ability to assign extra attributes while creating the parser object.

Returns

a metaparser object

Examples

>>> from xbu_shared.parser.nxos.show_version import ShowVersion
>>> p = ShowVersion()

<parser.nxos.show_version.ShowVersion object at 0xf6e0ec6c>

Class variables:

schema (dict): defines the common data structure among all types of

device output (cli, xml, yang) current metaparser supports.

key_traceable(‘bool’): enable the parser output key usage tracing

functionality, default value is ‘False’

CONTEXT_LIST (tuple): static variable defines valid contexts

DEFAULT_CONTEXT (str): constant variable with value ‘cli’

class initialization - set attributes for the parser object according to user’s input.

parsed_output (dicts): holds the raw output before the filtering

schema = None

command = None

key_traceable = False

CONTEXT_LIST = ('cli', 'xml', 'yang', 'rest')

DEFAULT_CONTEXT = 'cli'

call_parser(context)

This function returns the object context and raise an attribute error if not found.

parse_selected_keys(selected_keys, output, **kwargs)

This function retrieves the corresponding selected_keys portion of the parsed output.

parse(*, selected_keys=None, context=None, ignore_update=True, warn_unsupported_keys=None, **kwargs)

public method for users to call to execute a parser

API runs correct parsing methods according to the ‘context’ user specific in the constructor.

Procedure of parse function:

1.Select specific parsing mechanism (cli(), xml(), yang()) based on ‘context’ input. Each parsing mechanism defined in subclass parser object should include 3 steps: - Get the output from the device - Run existing parser or self implemented parser with the output - Transform the output into ‘schema’ compatible dictionary and return. Detail steps to implement parsing mechanism please read template.py within the package.

2.Schema checking - metaparser will do schema checking to make sure the parsing mechanism returns correct data structure.

3.Apply user defined filter on output, only selected key-value pairs will be returned as the original format from the output.

Parameters

• selected_keys (list) –

  keyword-only arg, a filtering mechanism which allows user to select desired keys (nested keys) from the raw parser output and reform a new dict containing only those selected key-value pairs.

  selected_keys can be a list of list or a list of tuple which contains flattened nested keys from the output dictionary. Python regular expression pattern can be used to define matching key format.

  For example: selected_keys =

  [[‘a’, ‘b’], [r’.*’, ‘c’], [r’^d’, r’.*’]]

  Here ‘r’ in front of the key string indicates the ‘raw string literal’ used as the Python regexp pattern.

• warn_unsupported_keys (bool) – Log warning instead of raising an exception when unsupported keys are found.

• kwarg (dict) – gives the user ability to pass extra parameters.

Returns

a nested dict obj

Example

>>> parser = ShowVersion(device=uut, context='xml')

get the entire output

>>> output = parser.parse()

get the output only contains specific keys selected by users

>>> selected_keys = [['hardware', 'bootflash'],
                     [r'.*', 'kickstart'],
                     ['reason'],
                     [r'^kernel', r'.*']]

>>> output = parser.parse(selected_keys = selected_keys)

>>> {'hardware':      {'bootflash': '2048256'},
     'kernel_uptime': {'days': '113',
                       'hours': '2',
                       'minutes': '42',
                       'seconds': '5'},
     'reason':       'Unknown',
     'software':     {'kickstart': 'version 6.2(6)',
                      'kickstart_compile_time': '12/5/2013',
        'kickstart_image_file': 'bootflash:///kickstart.6.2.bin'}}

tracer = {}

genie.metaparser._metaparser.tclparser(pkgrequire)

genie.metaparser._metaparser.enable_key_usage_trace(section)

method to enable the global traceability of parser output key usage

This module method designed to be used as a pyats pre-processor

genie.metaparser._metaparser.log_key_usage_trace(section)

method to log overall parser output key usage

This module method designed to be used as a pyats post-processor