How does python bytecode works?

Kushal Kumaran kushal.kumaran+python at
Mon Jun 18 08:08:53 CEST 2012

On Mon, Jun 18, 2012 at 1:23 AM, Devin Jeanpierre
<jeanpierreda at> wrote:
> On Sun, Jun 17, 2012 at 5:54 AM, gmspro <gmspro at> wrote:
>> We know python is written in C.
>> C is not portable.
> Badly written C is not portable. But C is probably the most portable
> language on the planet, by virtue of basically every system having a C
> compiler backend.
> The issue is that a lot of people make nonportable assumptions about
> C, and runtimes / OSes / architectures are free to make lots of very
> weird decisions.
> For example, this code is not strictly universally-compatible C. It is
> "portable" in that the changes required to make it run on any system
> are trivial, but not in the sense that it should be able to compile
> without any changes. (Not unless a cheeky/smart compiler is involved,
> anyway).
> int main () {
>    return 0;
> }
> Instead of 0, it should "technically" return EXIT_SUCCESS AIUI. Most
> people don't care because EXIT_SUCCESS is 0 almost everywhere.

In the interests of pedantry, I will point out that the C standard
requires implementation to treat both 0 and EXIT_SUCCESS to be treated
as successful exits.  The implementation must translate this to
whatever the environment treats as successful termination of the
program.  Ref: specification of the exit(int) function.

>> So how does python work on a webserver like apache/httpd for a python
>> website?
>> How does the intermediate language communicate with server without
>> compiling python code?
> Apache is written in C, and can embed CPython. This is easy enough,
> because CPython is written in C, and C works well with other C code.
> CPython itself can communicate with Python code, because it is
> directly responsible for running Python code. So the server
> communicates with CPython, and CPython communicates with the Python
> code. At no time does Python code ever "directly" touch anything other
> than the interpreter.
> The bytecode doesn't really have much to do with all this, except that
> it is the specific thing that CPython works with.


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