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Mimics Fortran textual IO in Python

Project description

FORTRAN format interpreter for Python

Generates text from a Python list of variables or will read a line of text into Python variables according to the FORTRAN format statement passed.

To read Fortran records,

import fortranformat as ff
header_line = FortranRecordReader('(A15, A15, A15)')'              x              y              z')
['              x', '              y', '              z']
line = FortranRecordReader('(3F15.3)')'          1.000          0.000          0.500')
# Returns [1.0, 0.0, 0.5]'          1.100          0.100          0.600')
# Returns [1.1, 0.1, 0.6]

To write Fortran records,

import fortranformat as ff
header_line = FortranRecordWriter('(A15, A15, A15)')
header_line.write(['x', 'y', 'z'])
# Results in '              x              y              z'
line = FortranRecordWriter('(3F15.3)')
line.write([1.0, 0.0, 0.5])
# Results in '          1.000          0.000          0.500'
line.write([1.1, 0.1, 0.6])
# Results in '          1.100          0.100          0.600'

For more detailed usage, see the guide.


  • At present the library mimics the IO of the Intel FORTRAN compiler v.9.1 run on a Linux system. Differences to other FORTRAN compilers and platforms are generally minor.
  • The library should run on Python versions from at least 2.7


Generating the tests for a FORTRAN compiler

Characterisations for a selection of FORTRAN compilers already exists, but if you want to characterise a new compiler, do the following ...

  1. Configure the compile string under compilertests target for your particular FORTRAN compiler e.g. gfortran %s -o %s where %s is the input and output file placeholders respectively
  2. Configure the compiler tag under compilertests e.g. gfortran_10_2_0_osx_intel this is just used for naming although would advise to sticking to alphanumerics and underscores
  3. Run make compilertests. This generates, compiles and executes hundreds of combinations of edit descriptor in the FORTRAN compiler under test and saves the results in the .test files under the build directories.
  4. Move the .test files to an appropriate new location under tests/autogen/[input/output] into directories named raw
  5. Run make buildtests to generate Python test files based on the generated .test files

Running tests

Build the tests using

make buildtests

Make sure that pytest is installed then run using

make runtests

Note that some of the F output edit descriptors fail due to limitations in floating point number representation

To run a reduced test suite where time and resources are limited, use the following

make runminimaltests

Deploying a new package version

Update versions in and


To create a local build to test run ...

python build sdist --formats=gztar

To upload a version to PyPI run ...

python sdist
twine upload dist/<new version>


Although the library has a large body of automatically generated test code behind it, it has not been extensively user tested. Bug reports are welcome!

Please report bugs to,

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