http://hg.python.org/cpython/rev/00fdd8b1e17b changeset: 73843:00fdd8b1e17b branch: 3.2 parent: 73841:01292dd6dadd user: Antoine Pitrou <solipsis@pitrou.net> date: Sat Dec 03 22:56:02 2011 +0100 summary: Reformulate answer, and remove off-topic discussion of bytecode in a question about compiling to C. files: Doc/faq/design.rst | 49 +++++++++++---------------------- 1 files changed, 17 insertions(+), 32 deletions(-) diff --git a/Doc/faq/design.rst b/Doc/faq/design.rst --- a/Doc/faq/design.rst +++ b/Doc/faq/design.rst @@ -380,11 +380,24 @@ Can Python be compiled to machine code, C or some other language? ----------------------------------------------------------------- -Not easily. Python's high level data types, dynamic typing of objects and +Practical answer: + +`Cython <http://cython.org/>`_ and `Pyrex <http://www.cosc.canterbury.ac.nz/~greg/python/Pyrex/>`_ +compile a modified version of Python with optional annotations into C +extensions. `Weave <http://www.scipy.org/Weave>`_ makes it easy to +intermingle Python and C code in various ways to increase performance. +`Nuitka <http://www.nuitka.net/>`_ is an up-and-coming compiler of Python +into C++ code, aiming to support the full Python language. + +Theoretical answer: + + .. XXX not sure what to make of this + +Not trivially. Python's high level data types, dynamic typing of objects and run-time invocation of the interpreter (using :func:`eval` or :func:`exec`) -together mean that a "compiled" Python program would probably consist mostly of -calls into the Python run-time system, even for seemingly simple operations like -``x+1``. +together mean that a naïvely "compiled" Python program would probably consist +mostly of calls into the Python run-time system, even for seemingly simple +operations like ``x+1``. Several projects described in the Python newsgroup or at past `Python conferences <http://python.org/community/workshops/>`_ have shown that this @@ -395,34 +408,6 @@ from the `1997 Python conference <http://python.org/workshops/1997-10/proceedings/>`_ for more information.) -Internally, Python source code is always translated into a bytecode -representation, and this bytecode is then executed by the Python virtual -machine. In order to avoid the overhead of repeatedly parsing and translating -modules that rarely change, this byte code is written into a file whose name -ends in ".pyc" whenever a module is parsed. When the corresponding .py file is -changed, it is parsed and translated again and the .pyc file is rewritten. - -There is no performance difference once the .pyc file has been loaded, as the -bytecode read from the .pyc file is exactly the same as the bytecode created by -direct translation. The only difference is that loading code from a .pyc file -is faster than parsing and translating a .py file, so the presence of -precompiled .pyc files improves the start-up time of Python scripts. If -desired, the Lib/compileall.py module can be used to create valid .pyc files for -a given set of modules. - -Note that the main script executed by Python, even if its filename ends in .py, -is not compiled to a .pyc file. It is compiled to bytecode, but the bytecode is -not saved to a file. Usually main scripts are quite short, so this doesn't cost -much speed. - -.. XXX check which of these projects are still alive - -There are also several programs which make it easier to intermingle Python and C -code in various ways to increase performance. See, for example, `Cython -<http://cython.org/>`_, `Pyrex -<http://www.cosc.canterbury.ac.nz/~greg/python/Pyrex/>`_ and `Weave -<http://www.scipy.org/Weave>`_. - How does Python manage memory? ------------------------------ -- Repository URL: http://hg.python.org/cpython