Command Line Interface

This file shows some use case of Pythran on the command line.

Firstly lets clear the working space:

$> rm -f cli_*

One of the most classic use case in Pythran is to generate a native .so module:

$> printf '#pythran export foo()\n#pythran export msg\nmsg = \"hello world\"\ndef foo(): print(msg)' > cli_foo.py
$> pythran cli_foo.py -o cli_foo.so
$> ls cli_foo.so
cli_foo.so

The generated native .so module can then be used with the Python interpreter:

$> python -c 'import cli_foo ; cli_foo.foo()'
hello world
$> python -c 'import cli_foo ; print(cli_foo.msg)'
hello world

Pythran version can be dumped through --version:

$> pythran --version 2>&1
0.11.0.dev0

The module-level __pythran__ variable indicates that the module loaded has been pythranized:

$> python -c 'import cli_foo ; print(hasattr(cli_foo, \"__pythran__\"))'
True

You can choose your optimization level by using -O flag:

$> rm cli_foo.so
$> pythran cli_foo.py -O2 -o cli_foo.so
$> ls cli_foo.so
cli_foo.so

Out of curiosity, you can check the generated output:

$> pythran -E cli_foo.py

That’s some heavily templated code ;-) Pythran can then compile it for you to a Python module:

$> pythran cli_foo.cpp -o cli_foo.so

Pythran can also generate raw C++ code, using the -e switch:

$> printf 'msg = \"hello world\"\ndef foo(): print(msg)' > cli_foo.py
$> pythran -e cli_foo.py -o cli_foo.hpp
$> printf '#include \"cli_foo.hpp\"\nusing namespace __pythran_cli_foo ; int main() { foo()(); return 0 ; }' > cli_foo.cpp
$> `pythran-config --compiler --cflags` -std=c++11 cli_foo.cpp -o cli_foo
$> ./cli_foo
hello world

You can use -p option to apply a Pythran optimization. For example, the python code can propagate constants using the Pythran ConstantFolding optimization:

$> pythran -e cli_foo.py -p pythran.optimizations.ConstantFolding

If you want to specify the path of generated file:

$> pythran cli_foo.py -o /tmp/cli_foo.so -DNDEBUG
$> ls /tmp/cli_foo.so
/tmp/cli_foo.so

To know more options about Pythran, you can check:

$> pythran --help
usage: pythran [-h] [-o OUTPUT_FILE] [-P] [-E] [-e] [-v] [-w] [-V] [-p pass]
               [-I include_dir] [-L ldflags] [-D macro_definition]
               [-U macro_definition] [--config config] [-ftime-report]
               input_file

pythran: a python to C++ compiler

positional arguments:
  input_file           the pythran module to compile, either a .py or a .cpp
                       file

optional arguments:
  -h, --help           show this help message and exit
  -o OUTPUT_FILE       path to generated file. Honors %{ext}.
  -P                   only run the high-level optimizer, do not compile
  -E                   only run the translator, do not compile
  -e                   similar to -E, but does not generate python glue
  -v                   be more verbose
  -w                   be less verbose
  -V, --version        show program's version number and exit
  -p pass              any pythran optimization to apply before code
                       generation
  -I include_dir       any include dir relevant to the underlying C++ compiler
  -L ldflags           any search dir relevant to the linker
  -D macro_definition  any macro definition relevant to the underlying C++
                       compiler
  -U macro_definition  any macro undef relevant to the underlying C++ compiler
  --config config      config additional params
  -ftime-report        report time spent in each optimization/transformation

It's a megablast!