[FIXED] Error in python asterisk syntax. No idea what is wrong

Issue

I'm trying to locally minimize a complicated function using scipy.optimize.minimize. Since I require good gradients in order for the local optimization to be smoothily performed, but the function is so very much complicated in order for the derivatives to be written by hand, I decided to use Autoptim as the middle-man to handle my optimization using the automatic differentiation package Autograd to obtain the gradients.

After I installed the package (as well as Autograd), I opened my python terminal in order to run a few preliminary tests to check whether the installation and the package integration between scipy, autograd and autoptim went smoothily. Then Autoptim raised an error immediately upon import (at the line import autoptim). Since the interpreter gives the full stack of Exceptions raised, I went to the deeper layers to see what line initiated the cascade that halted the interpreter.

The line I found was line 88 of autoptim.py:

87. optim_vars = _convert_to_tuple(optim_vars)
88. precon_optim_vars = precon_fwd(*optim_vars,*args)
89. n_args = len(args)

Python interpreter raised an Invalid Syntax Exception, which means that something in that line is not written "in Python". I checked to see whether there was some unclosed parenthesis and that was not the case. I am using Python 3 so I figured that maybe something on that line was written in Python 2 syntax and it registers wrong for a Python 3 interpreter but as I understand it, the differences between the two versions is quite small and there is some (although not complete) retrocompatibility between the two.

So what gives? What am I missing here?

What is wrong with that line?

Here is the traceback of the import line in the python interpreter

>>> import autoptim
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.4/dist-packages/autoptim/__init__.py", line 6, in <module>
    from .autoptim import minimize  # noqa
  File "/usr/local/lib/python3.4/dist-packages/autoptim/autoptim.py", line 95
    return objective_function(*optim_vars, *args)
                                           ^
SyntaxError: invalid syntax

Solution

The syntax being used wasn't introduced until Python 3.5 (see PEP 448). You are using Python 3.4.

As a workaround, you could explicitly build the required list to unpack:

return objective_function(*list(optim_vars + args))

Answered By - chepner