Step-by-step exec

[saju.pillai at gmail.com]

On Nov 6, 4:27 pm, gregory.liel... at gmail.com wrote:
> Hi,
>
> I am using a small python file as an input file (defining constants,
> parameters, input data, ...) for a python application.
> The input file is simply read by an exec statement in a specific
> dictionary, and then the application retrieve all the data it need
> from the dictionary...
> Everything is working nicely, but I'd like to have something a little
> bit more robust regarding input file errors: now
> any error in the python input script raise an exception and stop the
> execution.
> What I am trying to do is to execute it "step-by-step", so that I can
> capture the exception if one line (or multi-line statement) fails,
> print a warning about the failure, and continue the execution fo the
> following lines/statements. Of course, an error on one line can
> trigger errors in the following lines, but it does not matter in the
> application I have in mind, the goal is to parse as much of the input
> script as possible, warn about the errors, and check what's inside the
> dictionary after the exec.
> One way to do it is to read the input script line per line, and exec
> each line in turn. However, this is not convenient as it does not
> allow multi-line statements, or basic control flow like if - else
> statements or loops.

Do you have control over the input file generation ? If the input file
can be easily divided into self sufficient blocks of code, you could
read each block in one at a time and do a compile() and exec(). Your
input file need not be a full python script too, you could just have
token delimited blocks of python code which are read in 1 block at a
time and then exec().

-srp

>
> Is there a better way for a step-by-step exec? Syntax errors in the
> input script are not really a problem (as it is generated elsewhere,
> it is not directly edited by users), although it would be nice to
> catch. The biggest problem are runtime errors (attribute error, value
> error, ...). Maybe compiling the file into a code object, and
> executing this code object step-by-step in a way similar to debug? pdb
> module should do something similar....
>
> Best regards,
>
> Greg.