用Python评估数学表达式 [英] Evaluating mathematical expressions in Python

问题描述

我想将给定的数学表达式标记成这样的解析树:

I want to tokenize a given mathematical expression into a parse tree like this:

((3 + 4 - 1) * 5 + 6 * -7) / 2

                          '/'
                        /     \
                       +        2
                    /     \
                  *         *
                /   \     /   \
               -     5   6     -7
             /   \
            +     1
          /   \
         3     4

是否有任何纯Python方法可以做到这一点?就像以字符串形式传递给Python，然后像上面提到的那样以树的形式返回.

Is there any pure Python way to do this? Like passing as a string to Python and then get back as a tree like mentioned above.

谢谢.

推荐答案

是的，Python 模块提供了执行此操作的工具.您必须为您的Python版本查找确切的接口，因为ast模块似乎定期更改.

Yes, the Python ast module provides facilities to do this. You'll have to look up the exact interface for your version of Python, since the ast module seems to change regularly.

尤其是 ast.parse() 方法将有助于您的应用程序:

In particular, the ast.parse() method will be helpful for your application:

>>> import ast
>>> ast.parse("(1+2)*3", "", "eval")
<_ast.Expression object at 0x88950>
>>> ast.dump(_)
'Expression(body=BinOp(left=BinOp(left=Num(n=1), op=Add(), right=Num(n=2)), op=Mult(), right=Num(n=3)))'

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