Checking for sympy expr equality for evaluate=False

struct_eq.py

from sympy import sympify, default_sort_key

def struct_eq(expr1, expr2):
    '''
    Tests that two expressions are structurally equal without regard to the evaluate flag.
    This is done by manually recursing through all the args until we get to a base case.
    When building an expression with the evaluate flag, args are not ordered
    so we must manually check the struture without regard to argument order.
    '''
    if expr1 == expr2:  # if it passes usual test, return true to save time
        return True
    if expr1.func != expr2.func:  # top level func check...
        return False
    if expr1.is_Atom or expr2.is_Atom:  # here is our base case...
        return expr1 == expr2
    if len(expr1.args) != len(expr2.args):  # need this check so we can zip
        return False
    sorted1 = sorted(expr1.args, key=default_sort_key)
    sorted2 = sorted(expr2.args, key=default_sort_key)
    return all(struct_eq(arg1, arg2) for arg1, arg2 in zip(sorted1, sorted2))

if __name__ == '__main__':
    e1, e2 = sympify('2*x + 3*x - 4', evaluate=False), sympify('3*x + 2*x - 4', evaluate=False)
    struct_eq(e1, e2)