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Safer way to sympify unsanitized input

Project description

Safer Sympify

Convert unsanitized user input into SymPy expression.

This does not prevent all possible attacks. However, this is much safer than using eval(), which SymPy still does.

See SymPy PR12524 for more details:


    Create a SymPy expression from user input. 
    This uses pure Python syntax. 
    Whitelisted operators and functions only are allowed.
    >>> expr = SaferSympify().str2sympy('-sqrt(1 + a**b*b)/((a**b)*b+1)')
    >>> expr
    -1/sqrt(a**b*b + 1)

    Get free symbols:
    >>> sorted(expr.free_symbols, key=lambda x: str(x))
    [a, b]

    Evaluate expression:
    >>> expr.evalf(subs={'a': 1, 'b': 3, 'c': 5})  # Note extra values can be passed too

    Simplify expression:
    >>> expr.simplify()
    -1/sqrt(a**b*b + 1)

    Pretty-print expression as Latex (could be displayed in browser with MathJax)
    >>> sympy.latex(expr)
    '- \\frac{1}{\\sqrt{a^{b} b + 1}}'

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