### Table Of Contents

- Using F2PY
  - Command `f2py`
  - Python module `f2py2e`

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Using via `numpy.distutils`

# Using F2PY

F2PY can be used either as a command line tool `f2py` or as a Python module `f2py2e`.

## Command `f2py`

When used as a command line tool, `f2py` has three major modes, distinguished by the usage of `-c` and `-h` switches:

1. To scan Fortran sources and generate a signature file, use

       f2py -h <filename.pyf> <options> <fortran files>   \
         [[ only: <fortran functions>  : ]                \
          [ skip: <fortran functions>  : ]]...            \
         [<fortran files> ...]

   Note that a Fortran source file can contain many routines, and not necessarily all routines are needed to be used from Python. So, you can either specify which routines should be wrapped (in `only: .. :` part) or which routines F2PY should ignored (in `skip: .. :` part).

   If `<filename.pyf>` is specified as `stdout` then signatures are send to standard output instead of a file.

   Among other options (see below), the following options can be used in this mode:

   `--overwrite-signature`

     Overwrite existing signature file.

2. To construct an extension module, use

       f2py <options> <fortran files>          \
         [[ only: <fortran functions>  : ]     \
          [ skip: <fortran functions>  : ]]... \
         [<fortran files> ...]

   The constructed extension module is saved as `<modulename>module.c` to the current directory.

   Here `<fortran files>` may also contain signature files. Among other options (see below), the following options can be used in this mode:

   `--debug-capi`

     Add debugging hooks to the extension module. When using this extension module, various information about the wrapper is printed to standard output, for example, the values of variables, the steps taken, etc.

   `-include'<includefile>'`

     Add a CPP `#include` statement to the extension module source. `<includefile>` should be given in one of the following forms:

         "filename.ext"
         <filename.ext>

     The include statement is inserted just before the wrapper functions. This feature enables using arbitrary C functions (defined in `<includefile>`) in F2PY generated wrappers.

     This option is deprecated. Use `usercode` statement to specify C code snippets directly in signature files

   `--[no-]wrap-functions`

   > Create Fortran subroutine wrappers to Fortran functions. `--wrap-functions` is default because it ensures maximum portability and compiler independence.

   `--include-paths <path1>:<path2>:..`

     Search include files from given directories.

   `--help-link [<list of resources names>]`

     List system resources found by `numpy_distutils/system_info.py`. For example, try `f2py --help-link lapack_opt`.

3. To build an extension module, use

       f2py -c <options> <fortran files>       \
         [[ only: <fortran functions>  : ]     \
          [ skip: <fortran functions>  : ]]... \
         [ <fortran/c source files> ] [ <.o, .a, .so files> ]

   If `<fortran files>` contains a signature file, then a source for an extension module is constructed, all Fortran and C sources are compiled, and finally all object and library files are linked to the extension module `<modulename>.so` which is saved into the current directory.

   If `<fortran files>` does not contain a signature file, then an extension module is constructed by scanning all Fortran source codes for routine signatures.

   Among other options (see below) and options described in previous mode, the following options can be used in this mode:

   `--help-fcompiler`

     List available Fortran compilers.

   `--help-compiler` [depreciated]

     List available Fortran compilers.

   `--fcompiler=<Vendor>`

     Specify Fortran compiler type by vendor.

   `--f77exec=<path>`

     Specify the path to F77 compiler

   `--fcompiler-exec=<path>` [depreciated]

     Specify the path to F77 compiler

   `--f90exec=<path>`

     Specify the path to F90 compiler

   `--f90compiler-exec=<path>` [depreciated]

     Specify the path to F90 compiler

   `--f77flags=<string>`

     Specify F77 compiler flags

   `--f90flags=<string>`

     Specify F90 compiler flags

   `--opt=<string>`

     Specify optimization flags

   `--arch=<string>`

     Specify architecture specific optimization flags

   `--noopt`

     Compile without optimization

   `--noarch`

     Compile without arch-dependent optimization

   `--debug`

     Compile with debugging information

   `-l<libname>`

     Use the library `<libname>` when linking.

   `-D<macro>[=<defn=1>]`

     Define macro `<macro>` as `<defn>`.

   `-U<macro>`

     Define macro `<macro>`

   `-I<dir>`

     Append directory `<dir>` to the list of directories searched for include files.

   `-L<dir>`

     Add directory `<dir>` to the list of directories to be searched for `-l`.

   `link-<resource>`

   > Link extension module with <resource> as defined by `numpy_distutils/system_info.py`. E.g. to link with optimized LAPACK libraries (vecLib on MacOSX, ATLAS elsewhere), use `--link-lapack_opt`. See also `--help-link` switch.

   When building an extension module, a combination of the following macros may be required for non-gcc Fortran compilers:

       -DPREPEND_FORTRAN
       -DNO_APPEND_FORTRAN
       -DUPPERCASE_FORTRAN

   To test the performance of F2PY generated interfaces, use `-DF2PY_REPORT_ATEXIT`. Then a report of various timings is printed out at the exit of Python. This feature may not work on all platforms, currently only Linux platform is supported.

   To see whether F2PY generated interface performs copies of array arguments, use `-DF2PY_REPORT_ON_ARRAY_COPY=<int>`. When the size of an array argument is larger than `<int>`, a message about the coping is sent to `stderr`.

Other options:

`-m <modulename>`
  Name of an extension module. Default is `untitled`. Don’t use this option if a signature file (*.pyf) is used.
`--[no-]lower`
  Do [not] lower the cases in `<fortran files>`. By default, `--lower` is assumed with `-h` switch, and `--no-lower` without the `-h` switch.
`--build-dir <dirname>`
  All F2PY generated files are created in `<dirname>`. Default is `tempfile.mkdtemp()`.
`--quiet`
  Run quietly.
`--verbose`
  Run with extra verbosity.
`-v`
  Print f2py version ID and exit.

Execute `f2py` without any options to get an up-to-date list of available options.

## Python module `f2py2e`

Warning

The current Python interface to `f2py2e` module is not mature and may change in future depending on users needs.

The following functions are provided by the `f2py2e` module:

`run_main(<list>)`

  Equivalent to running:

      f2py <args>

  where `<args>=string.join(<list>,' ')`, but in Python. Unless `-h` is used, this function returns a dictionary containing information on generated modules and their dependencies on source files. For example, the command `f2py -m scalar scalar.f` can be executed from Python as follows

      >>> import f2py2e
      >>> r=f2py2e.run_main(['-m','scalar','docs/usersguide/scalar.f'])
      Reading fortran codes...
              Reading file 'docs/usersguide/scalar.f'
      Post-processing...
              Block: scalar
                              Block: FOO
      Building modules...
              Building module "scalar"...
              Wrote C/API module "scalar" to file "./scalarmodule.c"
      >>> print r
      {'scalar': {'h': ['/home/users/pearu/src_cvs/f2py2e/src/fortranobject.h'],
               'csrc': ['./scalarmodule.c',
                        '/home/users/pearu/src_cvs/f2py2e/src/fortranobject.c']}}

  You cannot build extension modules with this function, that is, using `-c` is not allowed. Use `compile` command instead, see below.

`compile(source, modulename='untitled', extra_args='', verbose=1, source_fn=None)`

  Build extension module from Fortran 77 source string `source`. Return 0 if successful. Note that this function actually calls `f2py -c ..` from shell to ensure safety of the current Python process. For example,

      >>> import f2py2e
      >>> fsource = '''
      ...       subroutine foo
      ...       print*, "Hello world!"
      ...       end
      ... '''
      >>> f2py2e.compile(fsource,modulename='hello',verbose=0)
      0
      >>> import hello
      >>> hello.foo()
       Hello world!