Raising python errors from Julia functions

[lassepe]

Some python package apis require the user the raise specific errors in certain scenarios. For example, Optuna requires the user to conditionally TrialPruned() error. In the current implementation of PythonCall, raising such errors from julia functions does not seem to be possible.

@pyeval `raise optuna.TrialPruned()`

fails with Python: SyntaxError: invalid syntax.

It would be handy to have a function like pyraise to throw such errors manually.

[cjdoris]

You want @pyexec (for executing arbitrary python code) not @pyeval (which evaluates a single expression):

julia> using PythonCall

julia> @pyeval `raise ValueError("hello")`
ERROR: Python: SyntaxError: invalid syntax (REPL[2]:1, line 1)

julia> @pyexec `raise ValueError("hello")`
ERROR: Python: ValueError: hello

[lassepe]

Nice, this works like charm! Thank you :)