f90wrap: Fortran to Python interface generator with derived type support
f90wrap is a tool to automatically generate Python extension modules which interface to Fortran code that makes use of derived types. It builds on the capabilities of the popular f2py utility by generating a simpler Fortran 90 interface to the original Fortran code which is then suitable for wrapping with f2py, together with a higher-level Pythonic wrapper that makes the existance of an additional layer transparent to the final user.
Copyright (C) James Kermode 2011-2018. Released under the GNU Lesser General Public License, version 3. Parts originally based on f90doc - automatic documentation generator for Fortran 90. Copyright (C) 2004 Ian Rutt.
If you would like to license the source code under different terms, please contact James Kermode email@example.com
- Python >= 2.7 or 3.x (both now supported!)
- Recent version of numpy which includes
- Fortran compiler - tested with
gfortran4.6+ and recent
For the latest stable release, install with either
pip install f90wrap
f90wrap can also be installed using
conda via the conda-forge channel:
conda config --add channels conda-forge
Once the conda-forge channel has been enabled, f90wrap can be installed with:
conda install f90wrap
For the development version, installation is as follows:
git clone https://github.com/jameskermode/f90wrap cd f90wrap python setup.py install [--prefix PREFIX]
Examples and Testing
To test the installation, run
make test from the
directory. You may find the code in the various examples useful.
f90wrap has been used to wrap the following large-scale scientific applications:
See this IPython notebook from a recent seminar for more details.
f90wrap to wrap a set of Fortran 90 source files and produce
wrappers suitable for input to f2py use:
f90wrap -m MODULE F90_FILES
MODULE is the name of the Python module you want to produce (e.g.
the name of the Fortran code you are wrapping) and
F90_FILES is a list
of Fortran 90 source files containing the modules, types and subroutines
you would like to expose via Python.
This will produce two types of output: Fortran 90 wrapper files suitable
for input to
f2py to produce a low-level Python extension module, and a
high-level Python module desinged to be used together with the
f2py-generated module to give a more Pythonic interface.
One Fortran 90 wrapper file is written for each source file, named
f90wrap_F90_FILE.f90, plus possibly an extra file named
f90wrap_toplevel.f90 if there are any subroutines or functions defined
outside of modules in
To use f2py to compile these wrappers into an extension module, use:
f2py -c -m _MODULE OBJ_FILES f90wrap_*.f90 *.o
_MODULE is the name of the low-level extension module.
Optionally, you can replace
f2py-f90wrap, which is a
slightly modified version of
f2py included in this distribution
that introduces the following features:
- Allow the Fortran
present()intrinsic function to work correctly with optional arguments. If an argument to an f2py wrapped function is optional and is not given, replace it with
- Allow Fortran routines to raise a RuntimeError exception with a
message by calling an external function
f90wrap_abort(). This is implemented using a
- Allow Fortran routines to be interrupted with
Ctrl+Cby installing a custom interrupt handler before the call into Fortran is made. After the Fortran routine returns, the previous interrupt handler is restored.
- Unlike standard
intent(in, out). This was a deliberate design decision to allow allocatable and automatic arrays of unknown output size to be used. It is hard in general to work out what size array needs to be allocated, so relying on the the user to pre-allocate from Python is the safest solution.
- Scalar arguments without
intentare treated as
f2py. To have
inoutscalars, you need to call
--default-to-inoutflag and declare the python variables as 1-length numpy arrays (
- Pointer arguments are not supported.
- Arrays of derived types are currently not fully supported: a workaround is provided for 1D-fixed-length arrays, i.e.
type(a), dimension(b) :: c. In this case, the super-type
Type_a_Xb_Arraywill be created, and the array of types can be accessed through
c.items. Note that dimension b can not be
:, but can be a parameter.
How f90wrap works
There are five steps in the process of wrapping a Fortran 90 routine to allow it to be called from Python.
- The Fortran source files are scanned, building up an abstract symbol tree (AST) which describes all the modules, types, subroutines and functions found.
- The AST is transformed to remove nodes which should not be wrapped (e.g. private symbols in modules, routines with arguments of a derived type not defined in the project, etc.)
f90wrap.f90wrapgen.F90WrapperGeneratorclass is used to write a simplified Fortran 90 prototype for each routine, with derived type arguments replaced by integer arrays containing a representation of a pointer to the derived type, in the manner described in (Pletzer2008)[http://link.aip.org/link/?CSENFA/10/86/1]. This allows opaque references to the true Fortran derived type data structures to be passed back and forth between Python and Fortran.
- f2py is used to combine the F90 wrappers and the original compiled functions into a Python extension module (optionally, f2py can be replaced by f2py-f90wrap, a slightly modified version which adds support for exception handling and interruption during exceution of Fortran code).
f90wrap.pywrapgen.PythonWrapperGeneratorclass is used to write a thin object-oriented layer on top of the f2py generated wrapper functions which handles conversion between Python object instances and Fortran derived-type variables, converting arguments back and forth automatically.
Additional command line arguments can be passed to f90wrap to customize
how the wrappers are generated. See the
examples/ directory to see how
some of the options are used:
-h, --help show this help message and exit -v, --verbose set verbosity level [default: None] -V, --version show program's version number and exit -p PREFIX, --prefix PREFIX Prefix to prepend to arguments and subroutines. -c [CALLBACK [CALLBACK ...]], --callback [CALLBACK [CALLBACK ...]] Names of permitted callback routines. -C [CONSTRUCTORS [CONSTRUCTORS ...]], --constructors [CONSTRUCTORS [CONSTRUCTORS ...]] Names of constructor routines. -D [DESTRUCTORS [DESTRUCTORS ...]], --destructors [DESTRUCTORS [DESTRUCTORS ...]] Names of destructor routines. -k KIND_MAP, --kind-map KIND_MAP File containing Python dictionary in f2py_f2cmap format -s STRING_LENGTHS, --string-lengths STRING_LENGTHS "File containing Python dictionary mapping string length names to values -S DEFAULT_STRING_LENGTH, --default-string-length DEFAULT_STRING_LENGTH Default length of character strings -i INIT_LINES, --init-lines INIT_LINES File containing Python dictionary mapping type names to necessary initialisation code -I INIT_FILE, --init-file INIT_FILE Python source file containing code to be added to autogenerated __init__.py -A ARGUMENT_NAME_MAP, --argument-name-map ARGUMENT_NAME_MAP File containing Python dictionary to rename Fortran arguments --short-names SHORT_NAMES File containing Python dictionary mapping full type names to abbreviations -m MOD_NAME, --mod-name MOD_NAME Name of output extension module (without .so extension). -M, --move-methods Convert routines with derived type instance as first agument into class methods -P, --package Generate a Python package instead of a single module -a ABORT_FUNC, --abort-func ABORT_FUNC Name of Fortran subroutine to invoke if a fatal error occurs --only [ONLY [ONLY ...]] Subroutines to include in wrapper --skip [SKIP [SKIP ...]] Subroutines to exclude from wrapper
James Kermode: firstname.lastname@example.org