SymPy - sympify() function

The sympify() function is used to convert any arbitrary expression such that it can be used as a SymPy expression. Normal Python objects such as integer objects are converted in SymPy. Integer, etc.., strings are also converted to SymPy expressions.

>>> expr="x**2+3*x+2" 
>>> expr1=sympify(expr) 
>>> expr1 
>>> expr1.subs(x,2)

The above code snippet gives the following output −

12

Any Python object can be converted in SymPy object. However, since the conversion internally uses eval() function, unsanitized expression should not be used, else SympifyError is raised.

>>> sympify("x***2")
---------------------------------------------------------------------------

SympifyError: Sympify of expression could not parse x***2 failed, because of exception being raised.

The sympify() function takes following arguments: * strict: default is False. If set to True, only the types for which an exppcit conversion has been defined are converted. Otherwise, SympifyError is raised. * evaluate: If set to False, arithmetic and operators will be converted into their SymPy equivalents without evaluating expression.

>>> sympify("10/5+4/2")

The above code snippet gives the following output −

4

>>> sympify("10/5+4/2", evaluate=False)

The above code snippet gives the following output −

$frac{10}{5}+frac{4}{2}$