Exceptions? Is it possible to catch SyntaxError event?

[Michał Pawłowski]

Hi.

I'd like to manage situation, when the formula, which I'd like to process has syntax error.

I tryied to use try except blocks, but its doesn't work, how can I achieve it?

#!/usr/bin/python3

from sympy import *

x = Symbol('x')

try:

    val_1 = x*sin(x)**2+x*cos(x)**2*

except SyntaxError:

    print('SyntaxError')

except:

    print('OtherError')

Thanks

Mike

[Michał Pawłowski]

Ok, I've found the solution!

I need to put the formula inside of quotes. And then pass it through simplify or expand functions.
The error will have such code:

OtherError:  <class 'sympy.core.sympify.SympifyError'>

Thanks

Mike

[Aaron Meurer]

It is not recommended to pass strings to SymPy functions like this.
Support for this will eventually be removed. If you want to convert a
string to a SymPy expression, it's better to pass it to sympify()
(note the different spelling from simplify()) first, like

expr = sympify('x*sin(x)**2+x*cos(x)**2')
expand(expr)

This will raise SympifyError if there is a syntax error, as you noted.

You can also use parse_expr() if you want more low-level control over
how strings are parsed.

Aaron Meurer

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