ParserModule

ParserModule(object)

This class represents the base object, from which other (vendor specific classes) inherit. This class provides basic set of functions which handle parsing of raw text outputs based on Python’s re module and regex strings provided by Patterns class.

The core idea behind ParserModule is that the complexity of various command outputs differ. Some outputs, such as ‘show mac address-table’ are simple enough to be handled by single regex pattern. On the other hand, some outputs, such as ‘show interfaces’ are way more complex and would require a very long and complex regex patterns to match. Also, every little change in the output would cause this pattern not to match. To avoid the usage of overly complex regex patterns, the parsing can be divided into two steps, or levels. In the first level, the text output is ‘pre-processed’, for example the output of show interfaces is splitted to list of strings, where each string represents a single interface. In the second level, each of these strings can be processed using multiple patterns, resulting in final dictionary representing the interface. For some outputs, these two levels can “overlap”, meaning that the first level can already return a dictionary, but some of the keys need to be ‘post-processed’ by the second level. A great example of such command is ‘show vlan brief’, where the first level returns a list of dictionaries with keys [“vlan_id”, “name”, “ports”]. The value of “`”ports”` (which is a string of all ports assigned to this VLAN) can be further processed by second level, which converts this string to a list of individual ports.

Base Functions

• match_single_pattern(self, text, pattern) - This function tries to match a single regex pattern on given text string. This function operates in two ‘modes’: with or without named groups in regex pattern. If pattern contains at least one named group (for example r"^(?P<name_of_the_group>.*)"), the function will return list of dictionaries, where each dictionary has “name_of_the_group” as key and whatever the .* matched as value. If pattern does not contain any named group, list of strings is returned, each string being one match of the pattern (basically re.findall(pattern=pattern, string=text)).
• update_entry(self, orig_entry, new_entry) - This function simply updates dict orig_entry with dict new_entry. The changes are made only for keys, that are not in the orig_entry or those, which value is None. The updated dictionary is returned.
• match_multi_pattern(self, text, patterns) - This function uses multiple regex patterns to match against given text. At the beginning, a new dictionary is created with named groups of ALL the patterns as keys and values None. Each time one of the patterns matches, the resulting dictionary is updated.
• _level_zero(self, text, patterns) - This function tries to match a pattern from patterns until a match is found. Then based on the self.match_single_pattern(**kwargs) returns either list of strings, or list of dictionaries. This function is used either for matching ‘simple’ outputs or for pre-processing (and post-processing) of more complex outputs.
• _level_one(self, text, command) - Given the command variable (which represents the command used to get output), it determines the level of the command and fetches corresponding patterns from self.patterns["level0"][command] (an instance of Patterns class). If the level is 0, it simply returns the output of self._level_zero(text, patterns). If the level is 1, it continues to process individual entries returned by _level_zero based on patterns from self.patterns["level1"][command]. Return a list of dictionaries.
• autoparse(self, text, command) - The main entry point for parsing, given just the text output and command it determines the proper way to parse the output and returns result.

class ParserModule(device_type, DEBUG=False)

Bases: object

This class provides necessary functions for parsing plaintext output of network devices. Uses patterns from PatternsLib for specified device type. The outputs are usually lists of dictionaries, which contain keys based on name groups of used regex patterns.

Parameters:

• device_type (str) – String representation of device type, such as cisco_ios
• DEBUG (bool) – Enables/disables debugging output

_level_one(text, command)

This function handles parsing of more complex plaintext outputs. First, the output of _level_zero() function is retrieved and then further parsed.

Parameters:

• text (str) – Plaintex output of given command, which will be parsed
• command (str) – Command string used to generate the output

Returns:

List of dictionaries

_level_zero(text, patterns)

This function handles parsing of less complex plaintext outputs, which can be parsed in one step.

Parameters:

• text (str) – Plaintex output which will be parsed
• patterns – List of compiled regex patterns, which are used to parse the text

Returns:

List dics (if patterns contain named groups) or list of strings (if they don’t)

autoparse(text, command)

The main entry point for parsing, given just the text output and command it determines the proper way to parse the output and returns result.

Parameters:

• text (str) – Text output to be processed
• command (str) – Command used to generate text output. Based on this parameter, correct regex patterns are selected.

Returns:

List of found entities, usually list of dictionaries

command_mapping(command)

This function determines the max_level of command - based on level of complexity of the output, the parsing is processed in 1 or 2 steps. Used for autoparse

Parameters:command (str) – Command used to generate the output, eg. show vlan brief Returns:(str) Highest level of specified command (top PatternsLib Key)

match_multi_pattern(text, patterns)

This functions tries to match multiple regex patterns against given text .

Parameters:

• text (str) – Text output to be processed
• patterns (lst) – List of re compiled patterns for parsing.

Returns:

Dictionary with names of all groups from all patterns as keys, with matching strings as values.

match_single_pattern(text, pattern)

This function tries to match given regex pattern against given text. If pattern contains named groups, list of dictionaries with these groups as keys is returned. If pattern does not contain any named groups, list of matching strings is returned.

Parameters:

• text (str) –
• pattern – re compiled regex pattern

Returns:

List of matches, either dictionaries or strings

update_entry(orig_entry, new_entry)

This function simply updates dictionary orig_entry with keys and values from new_entry. Only None values in orig_entry are updated. Keys with value None from new_entry are also used in order to ensure coherent output.

Parameters:

• orig_entry (dict) – Original dictionary to be updated based on entries in new_entry
• new_entry (dict) – New dictionary containing new data which should be added to orig_entry

Returns:

Updated dictionary

class CiscoIOSParser(DEBUG=False)

Bases: nuaal.Parsers.Parser.ParserModule

Child class of ParserModule designed for cisco_ios device type.

trunk_parser(text)

Function specifically designed for parsing output of show interfaces trunk command.

Parameters:text (str) – Plaintext output of show interfaces trunk command. Returns:List of dictionaries representing trunk interfaces.

vlanGroup_check(vlanGroup)