replacement for execfile

[Alex Popescu]

Hi all!

From another thread (and the pointed PEP) I have found that execfile will

not be present in Py3k. So, I am wondering what will be its replacement?
Considering that most probably Py3k will keep eval and exec, this will
still be possible (indeed requiring manual loading of the file string), so
I would really appreciate some enlightning comments on this.

Background:
Basically this question is related to my learning process/working project.
In this, I have the need to allow the final user to provide a configuration
like script, but built using my API (and whatever other normal Python code
they want). For this, having execfile was a nice surprise as I was able to
automatically expose the API (so the end user doesn't need to bother about
imports) and also easily execute it in the context I wanted.

many thanks in advance,
../alex

 

[Steven D'Aprano]

Hi all!

From another thread (and the pointed PEP) I have found that execfile
will not be present in Py3k. So, I am wondering what will be its
replacement? Considering that most probably Py3k will keep eval and
exec, this will still be possible (indeed requiring manual loading of
the file string), so I would really appreciate some enlightning comments
on this.

(1) Don't use eval, exec or execfile.

(2) If you're an expert, don't use eval, exec or execfile.

(3) If you're an expert, and are fully aware of the security risks, don't
use eval, exec or execfile.

(4) If you're an expert, and are fully aware of the security risks, and
have a task that can only be solved by using eval, exec or execfile, find
another solution.

(5) If there really is no other solution, you haven't looked hard enough.

(6) If you've looked REALLY hard, and can't find another solution, AND
you're an expert and are fully aware of the security risks, THEN you can
think about using eval, exec or execfile.

Background:
Basically this question is related to my learning process/working
project. In this, I have the need to allow the final user to provide a
configuration like script, but built using my API (and whatever other
normal Python code they want).

I hope this is running on their own computer, not yours.

If they're running it on a multi-user system, I hope they don't care about
security, because they probably don't have any now.

For this, having execfile was a nice surprise

Oh yes, I bet it was, in more ways than one.

as I was able to automatically expose the API (so the end user
doesn't need to bother about imports) and also easily execute it in the
context I wanted.

Let's see that I understand you... you're expecting the users to write
working Python code, but you think "import module" is too hard for them?

Anyway, with all the disclaimers above, execfile is trivial:


def execfile_(filename, globals_=None, locals_=None):
if globals_ is None:
globals_ = globals()
if locals_ is None:
locals_ = globals_
text = file(filename, 'r').read()
exec text in globals_, locals_

 

[Alex Popescu]

(1) Don't use eval, exec or execfile.

(2) If you're an expert, don't use eval, exec or execfile.

(3) If you're an expert, and are fully aware of the security risks,
don't use eval, exec or execfile.

(4) If you're an expert, and are fully aware of the security risks,
and have a task that can only be solved by using eval, exec or
execfile, find another solution.

(5) If there really is no other solution, you haven't looked hard
enough.

(6) If you've looked REALLY hard, and can't find another solution, AND
you're an expert and are fully aware of the security risks, THEN you
can think about using eval, exec or execfile.

Most probably I don't fit any of the aboves... but I still think that
the approach I am considering is quite correct .

I hope this is running on their own computer, not yours.

If they're running it on a multi-user system, I hope they don't care
about security, because they probably don't have any now.

Yes, the framework will be run by dev teams on their own computers, so
if somebody from that team would really want to rm something they will
not really need python scripts for it .

Let's see that I understand you... you're expecting the users to write
working Python code, but you think "import module" is too hard for
them?

That was just a cherry on the cake. The most important part is that
through this mechanism the user will be able to configure the framework
through normal Python code (very simple API: 3 functions), and not
through .ini, .xml or other variants.

Anyway, with all the disclaimers above, execfile is trivial:


def execfile_(filename, globals_=None, locals_=None):
if globals_ is None:
globals_ = globals()
if locals_ is None:
locals_ = globals_
text = file(filename, 'r').read()
exec text in globals_, locals_

Thanks for confirming my idea. But the question stands: even if I can
write myself an execfile equivalent, the same can apply to map, zip and
other functions that are provided by Python core. To bring it to the
extreme everything can be done at asm level, but we are chosing to use
high level languages. And for the moment I fail to see the reasons to
remove this function.

../alex

 

[Stefan Bellon]

(1) Don't use eval, exec or execfile.

Ok, then I would really like to ask a question about how to solve my
problem without execfile ... ;-)

I am embedding Python on Windows using MinGW. In order to execute a
Python script file, calling any of the PyRun_File functions does not
work but crashes (I assume this is because the Python DLL was built
using Microsoft tools and those tools and MinGW have different FILE
structures, so a FILE *fp cannot be passed from my MinGW C code to
the Python DLL).

Therefore my current solution is to call PyRun_String functions and
execute a string with the content "execfile('filename')".

Is there a way to solve this problem with PyRun_File?