syntax - Python: SyntaxError: keyword can't be an expression

43
votes

In a Python script I call a function from rpy2, but I get this error:

#using an R module 
res = DirichletReg.ddirichlet(np.asarray(my_values),alphas,
                              log=False, sum.up=False) 
SyntaxError: keyword can't be an expression

What exactly went wrong here?

5
pythonsyntaxsyntax-errorkeyword
Regarding your update: Many syntax errors come with a caret ^ pointing at the token that caused the parse error, others (including this one) don't. In any case, pay attention to the error message, and google the error messgae if necessary. In this case, the first hits should have cleared up things. - Sven Marnach
@SvenMarnach: Googling the error message brings you to this page now. - Thanatos

5 Answers

38
votes

sum.up is not a valid keyword argument name. Keyword arguments must be valid identifiers. You should look in the documentation of the library you are using how this argument really is called – maybe sum_up?

23
votes

I guess many of us who came to this page have a problem with Scikit Learn, one way to solve it is to create a dictionary with parameters and pass it to the model:

params = {'C': 1e9, 'gamma': 1e-07}
cls = SVC(**params)
8
votes

It's python source parser failure on sum.up=False named argument as sum.up is not valid argument name (you can't use dots -- only alphanumerics and underscores in argument names).

5
votes

Using the Elastic search DSL API, you may hit the same error with

s = Search(using=client, index="my-index") \
    .query("match", category.keyword="Musician")

You can solve it by doing:

s = Search(using=client, index="my-index") \
    .query({"match": {"category.keyword":"Musician/Band"}})
3
votes

I just got that problem when converting from % formatting to .format().

Previous code:

"SET !TIMEOUT_STEP %{USER_TIMEOUT_STEP}d" % {'USER_TIMEOUT_STEP' = 3}

Problematic syntax:

"SET !TIMEOUT_STEP {USER_TIMEOUT_STEP}".format('USER_TIMEOUT_STEP' = 3)

The problem is that format is a function that needs parameters. They cannot be strings. That is one of worst python error messages I've ever seen.

Corrected code:

"SET !TIMEOUT_STEP {USER_TIMEOUT_STEP}".format(USER_TIMEOUT_STEP = 3)