ParseError when parsing assignment expression

[lmwang9527]

When I parse an assignment expression, I am getting a "ParseError: leftover input after completed parse at index 1: ...=x+1...", while it works fine if I parse only the rhs of the assignment. Is this the expected behavior, or am I missing something? Thanks!

In [1]: from pymbolic import parse
   ...: parse("x+1")
Out[1]: Sum((Variable('x'), 1))

In [2]: parse("y=x+1")
---------------------------------------------------------------------------
ParseError                                Traceback (most recent call last)
<ipython-input-2-3431e375dd42> in <module>
----> 1 parse("y=x+1")

~/py3env/lib/python3.8/site-packages/pymbolic-2019.2-py3.8.egg/pymbolic/parser.py in __call__(se
lf, expr_str, min_precedence)
    536         result = self. parse_expression(pstate, min_precedence)
    537         if not pstate.is_at_end():
--> 538             pstate.raise_parse_error("leftover input after completed parse")
    539         return result
    540

~/py3env/lib/python3.8/site-packages/pytools-2019.1.1-py3.8.egg/pytools/lex.py in raise_parse_er
ror(self, msg)
    150             raise ParseError(msg, self.raw_string, None)
    151
--> 152         raise ParseError(msg, self.raw_string, self.lexed[self.index])
    153
    154     def expected(self, what_expected):

ParseError: leftover input after completed parse at index 1: ...=x+1...

[inducer]

Assignments are statements, not expressions (in Python, and also in general, with C being a prominent exception).

[lmwang9527]

Ahh, I hope you can forgive the stupid questions from a novice.

[inducer]

So pymbolic cannot parse statement? Thanks!

Nope. What you can do is use Python's parser library and process the expressions occurring there with pymbolic, as in this demo.

[lmwang9527]

Yes, I found the code snippet that does statement in the ast interop section of the pymbolic document. Thanks again!