使用pyparsing解析网络设备命令

时间：2019-03-14 01:33:14

标签： python parsing command-line pyparsing command-line-parsing

我正在使用pyparsing开发网络设备命令解析器。

我分析并定义了以下命令格式：

cli ::= string + (next)*
next ::= string|range|group|simple_recursive|selective_recursive|infinite_recursive|keywords
keywords ::= "WORD"
             | "LINE" 
             | "A.B.C.D" 
             | "A.B.C.D/M" 
             | "X:X::X:X" 
             | "X:X::X:X/M" 
             | "HH:MM:SS" 
             | "AA:NN" 
             | "XX:XX:XX:XX:XX:XX" 
             | "MULTILINE"
inner_recur ::= next + (next)* + ("|")* | ("|" + next + (next)*)*
string ::= alphanums + "_" + "-"
range ::= "<" + nums + "-" nums + ">"
group ::= "(" + inner_recur + ")"
simple_recursive ::= "." + range
selective_recursive ::= "{" + inner_recur + "}"
infinite_recursive ::= "[" + inner_recur + "]"

并以书面形式实施：

# string ::= alphanums + "_" + "-"
string_ = Word(alphanums + "_" + "-").setResultsName("string")
#print(string_.parseString("option82"))

# range ::= "<" + nums + "-" nums + ">"
range_ = Combine(Literal("<") + Word(nums) + Literal("-") + Word(nums) + Literal(">")).setResultsName("range")
#print(range_.parseString("<24-1004>"))

# simple_recursive ::= "." + range
simple_recursive_ = Combine(Literal(".") + range_).setResultsName("simple_recursive")
#print(simple_recursive_.parseString(".<1-60045>"))

# keywords ::= "WORD" | "LINE" | "A.B.C.D" | "A.B.C.D/M" | "X:X::X:X" | "X:X::X:X/M" | "HH:MM:SS" | "AA:NN" | "XX:XX:XX:XX:XX:XX" | "MULTILINE"
keywords_ = Keyword("X:X::X:X/M").setResultsName("X:X::X:/M") | Keyword("A.B.C.D/M").setResultsName("A.B.C.D/M") | Keyword("A.B.C.D").setResultsName("A.B.C.D") | Keyword("X:X::X:X").setResultsName("X:X::X:X") | Keyword("HH:MM:SS").setResultsName("HH:MM:SS") | Keyword("AA:NN").setResultsName("AA:NN") | Keyword("XX:XX:XX:XX:XX:XX").setResultsName("XX:XX:XX:XX:XX:XX") | Keyword("MULTILINE").setResultsName("MULTILINE") | Keyword("WORD").setResultsName("WORD") | Keyword("LINE").setResultsName("LINE")
#print(keywords_.parseString("A.B.C.D").asXML())


#next_ = Forward()
inner_recur = Forward()

# group ::= "(" + inner_recur + ")"
group_ = Combine(Literal("(") + inner_recur + Literal(")"))

# selective_recursive ::= "{" + inner_recur + "}"
selective_recursive_ = Combine(Literal("{") + inner_recur + Literal("}"))

# infinite_recursive ::= "[" + inner_recur + "]"
infinite_recursive_ = Combine(Literal("[") + inner_recur + Literal("]"))

# next ::= string|range|group|simple_recursive|selective_recursive|infinite_recursive|keywords
next_ = keywords_ | string_ | simple_recursive_ | range_ | group_ | selective_recursive_ | infinite_recursive_

# inner_recur ::= next + (next)* + ("|")* | ("|" + next + (next)*)*
inner_recur << next_ + ZeroOrMore(next_) + ZeroOrMore(Literal("|") | ZeroOrMore(Literal("|") + next_ + OneOrMore(next_)))

# cli ::= string + (next)*
cli_ = string_ + ZeroOrMore(next_)

为了测试解析器，我尝试输入数据

>>> test = cli_.parseString("bgp as .<1-200>")
>>> print(test)
>>> ['bgp', 'as', ['.<1-200>']]
test = cli_.parseString("bgp as <1-200> <1-255> <1-255> WORD A.B.C.D A.B.C.D/M (A|(B|C))")
print(test)
>>> 
test = cli_.parseString("test (A|<1-200>|(B|{a|b|c} aaa)")
test = cli_.parseString("test (A|<1-200>|(B|{a|b|c|})|)")

当解析第二个数据时，将引发无限递归。我不了解这种情况，没有任何解决方案...

我希望得到结果：

  

['bgp'，'as'，['<1-200>']，['<1-255>']，['<1-255>']，'WORD'，   'A.B.C.D'，'A.B.C.D / M'，['A'，['B'，'C']]]

我的格式或代码有什么问题？并修改点？

1 个答案:

答案 0 :(得分：0)

虽然您在编写代码之前已经用概念化的BNF术语定义语法迈出了良好的第一步，但我在理解语法方面还是有些挣扎。对我来说，罪魁祸首似乎就是这部分：

inner_recur ::= next + (next)* + ("|")* | ("|" + next + (next)*)*

从您发布的示例中，您似乎正在尝试使用'|'定义某种中缀表示法作为操作员。

从测试中看，您似乎还需要在任何分组（），[]或{}内支持多个inner_recur。

另外，请阅读文档（https://pyparsing-docs.readthedocs.io/en/latest/pyparsing.html）以更清楚地了解setResultsName和setName之间的区别。我很确定在整个解析器中，您使用的是setResultsName，但确实要使用setName。与您确实需要Combine时使用Group相似。

最后，我使用runTests重写了您的测试代码，发现您在第三项测试中不匹配（）。

这是您的解析器，具有以下更改：

# string ::= alphanums + "_" + "-"
string_ = Word(alphanums + "_" + "-").setResultsName("string")
#print(string_.parseString("option82"))

# range ::= "<" + nums + "-" nums + ">"
range_ = Group(Literal("<") + Word(nums) + Literal("-") + Word(nums) + Literal(">")).setResultsName("range")
#print(range_.parseString("<24-1004>"))

# simple_recursive ::= "." + range
simple_recursive_ = Group(Literal(".") + range_).setResultsName("simple_recursive")
#print(simple_recursive_.parseString(".<1-60045>"))

# keywords ::= "WORD" | "LINE" | "A.B.C.D" | "A.B.C.D/M" | "X:X::X:X" | "X:X::X:X/M" | "HH:MM:SS" | "AA:NN" | "XX:XX:XX:XX:XX:XX" | "MULTILINE"
keywords_ = Keyword("X:X::X:X/M").setResultsName("X:X::X:/M") | Keyword("A.B.C.D/M").setResultsName("A.B.C.D/M") | Keyword("A.B.C.D").setResultsName("A.B.C.D") | Keyword("X:X::X:X").setResultsName("X:X::X:X") | Keyword("HH:MM:SS").setResultsName("HH:MM:SS") | Keyword("AA:NN").setResultsName("AA:NN") | Keyword("XX:XX:XX:XX:XX:XX").setResultsName("XX:XX:XX:XX:XX:XX") | Keyword("MULTILINE").setResultsName("MULTILINE") | Keyword("WORD").setResultsName("WORD") | Keyword("LINE").setResultsName("LINE")
#print(keywords_.parseString("A.B.C.D").asXML())

#next_ = Forward()
inner_recur = Forward()

# group ::= "(" + inner_recur + ")"
group_ = Group(Literal("(") + OneOrMore(inner_recur) + Literal(")"))

# selective_recursive ::= "{" + inner_recur + "}"
selective_recursive_ = Group(Literal("{") + OneOrMore(inner_recur) + Literal("}"))

# infinite_recursive ::= "[" + inner_recur + "]"
infinite_recursive_ = Group(Literal("[") + OneOrMore(inner_recur) + Literal("]"))

# next ::= string|range|group|simple_recursive|selective_recursive|infinite_recursive|keywords
next_ = keywords_ | string_ | simple_recursive_ | range_ | group_ | selective_recursive_ | infinite_recursive_
#~ next_.setName("next_").setDebug()

# inner_recur ::= next + (next)* + ("|")* | ("|" + next + (next)*)*
#~ inner_recur <<= OneOrMore(next_) + ZeroOrMore(Literal("|")) | ZeroOrMore(Literal("|") + OneOrMore(next_))
inner_recur <<= Group(infixNotation(next_,
    [
        (None, 2, opAssoc.LEFT),
        ('|', 2, opAssoc.LEFT),
    ]) + Optional('|'))
# cli ::= string + (next)*
cli_ = string_ + ZeroOrMore(next_)


tests = """\
bgp as .<1-200>
bgp as <1-200> <1-255> <1-255> WORD A.B.C.D A.B.C.D/M (A|(B|C))
test (A|<1-200>|(B|{a|b|c} aaa))
test (A|<1-200>|(B|{a|b|c|})|)
"""
cli_.runTests(tests)

哪个给：

bgp as .<1-200>
['bgp', 'as', ['.', ['<', '1', '-', '200', '>']]]
- simple_recursive: ['.', ['<', '1', '-', '200', '>']]
  - range: ['<', '1', '-', '200', '>']
- string: 'as'


bgp as <1-200> <1-255> <1-255> WORD A.B.C.D A.B.C.D/M (A|(B|C))
['bgp', 'as', ['<', '1', '-', '200', '>'], ['<', '1', '-', '255', '>'], ['<', '1', '-', '255', '>'], 'WORD', 'A.B.C.D', 'A.B.C.D/M', ['(', [['A', '|', ['(', [['B', '|', 'C']], ')']]], ')']]
- A.B.C.D: 'A.B.C.D'
- A.B.C.D/M: 'A.B.C.D/M'
- WORD: 'WORD'
- range: ['<', '1', '-', '255', '>']
- string: 'as'


test (A|<1-200>|(B|{a|b|c} aaa))
['test', ['(', [['A', '|', ['<', '1', '-', '200', '>'], '|', ['(', [['B', '|', [['{', [['a', '|', 'b', '|', 'c']], '}'], 'aaa']]], ')']]], ')']]
- string: 'test'


test (A|<1-200>|(B|{a|b|c|})|)
['test', ['(', [['A', '|', ['<', '1', '-', '200', '>'], '|', ['(', [['B', '|', ['{', [['a', '|', 'b', '|', 'c'], '|'], '}']]], ')']], '|'], ')']]
- string: 'test'

在某些地方这可能不合时宜，但我希望它能为您提供一些想法，以推进您的项目。

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