84 lines
2.0 KiB
Python
84 lines
2.0 KiB
Python
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# Adapted from https://stackoverflow.com/a/9558001/2536294
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import ast
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from dataclasses import dataclass
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import operator as op
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from ._multiprocessing_helpers import mp
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if mp is not None:
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from .externals.loky.process_executor import _ExceptionWithTraceback
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# supported operators
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operators = {
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ast.Add: op.add,
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ast.Sub: op.sub,
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ast.Mult: op.mul,
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ast.Div: op.truediv,
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ast.FloorDiv: op.floordiv,
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ast.Mod: op.mod,
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ast.Pow: op.pow,
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ast.USub: op.neg,
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}
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def eval_expr(expr):
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"""
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>>> eval_expr('2*6')
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12
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>>> eval_expr('2**6')
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64
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>>> eval_expr('1 + 2*3**(4) / (6 + -7)')
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-161.0
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"""
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try:
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return eval_(ast.parse(expr, mode="eval").body)
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except (TypeError, SyntaxError, KeyError) as e:
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raise ValueError(
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f"{expr!r} is not a valid or supported arithmetic expression."
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) from e
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def eval_(node):
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if isinstance(node, ast.Constant): # <constant>
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return node.value
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elif isinstance(node, ast.BinOp): # <left> <operator> <right>
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return operators[type(node.op)](eval_(node.left), eval_(node.right))
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elif isinstance(node, ast.UnaryOp): # <operator> <operand> e.g., -1
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return operators[type(node.op)](eval_(node.operand))
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else:
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raise TypeError(node)
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@dataclass(frozen=True)
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class _Sentinel:
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"""A sentinel to mark a parameter as not explicitly set"""
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default_value: object
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def __repr__(self):
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return f"default({self.default_value!r})"
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class _TracebackCapturingWrapper:
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"""Protect function call and return error with traceback."""
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def __init__(self, func):
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self.func = func
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def __call__(self, **kwargs):
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try:
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return self.func(**kwargs)
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except BaseException as e:
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return _ExceptionWithTraceback(e)
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def _retrieve_traceback_capturing_wrapped_call(out):
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if isinstance(out, _ExceptionWithTraceback):
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rebuild, args = out.__reduce__()
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out = rebuild(*args)
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if isinstance(out, BaseException):
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raise out
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return out
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