Import/Create module from buffer

[Gruik]

Hi people,

I'm currently working on python embedding with C++. My goal is that
the C++ part handle files writing/reading so that the Python part only
works with buffers.

I succeeded in buffer exchanges. The problem is that some of the files
I read/write are python files so that, before embedding, I imported
them as modules when I needed them.

But now that the Python part only receive buffers, I can't do it
anymore. So I wonder :
- is it possible to import module from a buffer instead of files?
- or is it possible to create a module object from my buffer?

I looked on the Internet but didn't find anything about that. Does
anyone have an idea?

Thanks
Benjamin

 

[Gabriel Genellina]

I'm currently working on python embedding with C++. My goal is that
the C++ part handle files writing/reading so that the Python part only
works with buffers.

I succeeded in buffer exchanges. The problem is that some of the files
I read/write are python files so that, before embedding, I imported
them as modules when I needed them.

But now that the Python part only receive buffers, I can't do it
anymore. So I wonder :
- is it possible to import module from a buffer instead of files?
- or is it possible to create a module object from my buffer?

Yes, first compile the buffer to get a code object, then use PyImport_ExecCodeModule. See how this function is used in import.c

 

[Gruik]

Yes, first compile the buffer to get a code object, then use PyImport_ExecCodeModule. See how this function is used in import.c

Thanks for your quick answer !
I think I'll have no problem with that in C++ and I'm going to try it
right after this message.

But before that 1 question: what if I'm in Python ?
Following your solution, I did that in Python :

def load_buffer(buffer) :
compiled_buffer = compile(buffer, "module_name", "exec")
exec(compiled_buffer)

It works great except that I can't have a module object and that it is
as if I did "from module import *"
But I need the module object and not an "import *" behavior.
Any idea about the way to do that?

Benjamin

 

[Irmen de Jong]

But before that 1 question: what if I'm in Python ?
Following your solution, I did that in Python :

def load_buffer(buffer) :
compiled_buffer = compile(buffer, "module_name", "exec")
exec(compiled_buffer)

It works great except that I can't have a module object and that it is
as if I did "from module import *"
But I need the module object and not an "import *" behavior.
Any idea about the way to do that?

Something along the lines of:

import new
mymodule = new.module("mymodule")
exec <<<code>>> in mymodule.__dict__



--irmen

 

[Gruik]

Something along the lines of:

import new
mymodule = new.module("mymodule")
exec <<<code>>> in mymodule.__dict__

--irmen

Yeah it works !

exec(compiled_module, globals(), mymodule.__dict__)

Just to add mymodule to sys.modules and it's good!

Thanks again
Benjamin

 

[Gabriel Genellina]

Thanks for your quick answer !
I think I'll have no problem with that in C++ and I'm going to try it
right after this message.

But before that 1 question: what if I'm in Python ?
Following your solution, I did that in Python :

def load_buffer(buffer) :
compiled_buffer = compile(buffer, "module_name", "exec")
exec(compiled_buffer)

It works great except that I can't have a module object and that it is
as if I did "from module import *"
But I need the module object and not an "import *" behavior.
Any idea about the way to do that?

Almost - you have to create a new module and exec the code into its namespace:

py> import new
py> foo = new.module("foo", "This is the foo module")
py> exec "def f(): pass" in foo.__dict__
py> foo
<module 'foo' (built-in)>
py> foo.f
<function f at 0x00A3E230>
py> dir(foo)
['__builtins__', '__doc__', '__name__', 'f']

(replace "def f(): pass" with the compiled buffer)

Two differences with a "normal" module:

- it has no __file__ attribute - you may want to add it, with the original filename, or leave it off to show that it's not loaded from a file.
- it does not exist in sys.modules, so other modules cannot import it. If you want to allow that: sys.modules['foo'] = foo (perhaps one should check previously that there is no module named "foo" before replacing it...)