从无法使用 ast.literal_eval 解析的字符串解析嵌套列表 [英] Parse nested list from string that cannot be parsed with ast.literal_eval

问题描述

我将文件解析为 Python 列表，但遇到了这样的嵌套列表:

{ 1 4{ 2a 0.0 }{ 3 0.0 }{ 4c 0.0 }{ 5 0.0 } }

我想把它解释为一个列表，但嵌套了，所以我想成为这样的结果Python列表:

[1,4,[2a,0.0],[3,0.0],[4c,0.0],[5,0.0]]

我设法使用以下内容执行正确的字符串:

l = """{ 1 4{ 2 0.0 }{ 3 0.0 }{ 4 0.0 }{ 5 0.0 } }""";l = l.replace("{\t",",[").replace("\t}","]").replace("{","[").;).replace("}","]").replace("\t",",")[1:]

我也可以应用 l.strip("\t") 使它是一个列表，但不是嵌套的，否则它会被展平，这是我不想要的.

我尝试使用 ast.literal_eval(l)，但它在字符串上失败，例如2a

解决方案

Pyparsing 有一个内置的帮助器 nestedExpr 来帮助解析开始和结束分隔符之间的嵌套列表:

<预><代码>>>>导入pyparsing为pp>>>nested_braces = pp.nestedExpr('{', '}')>>>t = """{ 1 4{ 2a 0.0 }{ 3 0.0 }{ 4c 0.0 }{ 5 0.0 } }""">>>打印(nested_braces.parseString(t).asList())[['1', '4', ['2a', '0.0'], ['3', '0.0'], ['4c', '0.0'], ['5', '0.0']]]

I parse a file to a Python list and I encountered a nested list like this:

{   1   4{  2a  0.0 }{  3   0.0 }{  4c  0.0 }{  5   0.0 }   }

I want to interpret it as a list, yet nested, so I want to be the resulting Python list as follows:

[1,4,[2a,0.0],[3,0.0],[4c,0.0],[5,0.0]]

I manage to do a correct string of this with a following:

l = """{    1   4{  2   0.0 }{  3   0.0 }{  4   0.0 }{  5   0.0 }   }"""
l = l.replace("{\t",",[").replace("\t}","]").replace("{","[").replace("}","]").replace("\t",",")[1:]

I can also apply l.strip("\t") so that it is a list, but not for a nested, otherwise it will be flattened, which I do not want.

I tried with ast.literal_eval(l), but it fails on strings e.g. 2a

解决方案

Pyparsing has a built-in helper nestedExpr to help parse nested lists between opening and closing delimiters:

>>> import pyparsing as pp
>>> nested_braces = pp.nestedExpr('{', '}')
>>> t = """{   1   4{  2a  0.0 }{  3   0.0 }{  4c  0.0 }{  5   0.0 }   }"""
>>> print(nested_braces.parseString(t).asList())
[['1', '4', ['2a', '0.0'], ['3', '0.0'], ['4c', '0.0'], ['5', '0.0']]]

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