fort – The fort module

• Class fort.File

Suport for Python/Fortran interworking.

This module provides support for writing Python modules and programs that need to interwork with Fortran in various ways.

The main thing this module provides is the File class, which supports access to unformatted files; a binary file format.

The other main feature is the unpackRecord() function, which can be useful during the initial stages of converting a Fortran program to reasonably simliar looking Python code.

Classes

File

A Fortran binary (unformatted) file object.

A binary Fortran file can be opened using the open method of this module; a File object is returned that supports a writeline method (for writing records), a readline method (for reading records) and the iterator protocol (for reading).

It is normally easier to use the open() factory function rather than construct instances directly.

See fort.File for details

Functions

open(name, mode)

Open a binary Fortran file.

Return Value

A File instance for the newly opened file.

Arguments

name

The path of the file to be opened.

mode

The file’s access mode, as per the builtin open function. The default is ‘rb’ and must always include ‘b’.

unpackRecord(line, start, format)

A simple function to unpack Fortran formatted records.

The intention is to make translation of Fortran such as the following relatively striaghtforward:

read(line(2:64), '(i4,i5,a12,i4,a36)') lat, lon, sid, ht, name
read(line, '(i4,3i4,i4)') a, arr, b

In Python the above then becomes:

lat, lon, sid, ht, name = unpackRecord(line, 2, 'i4,i5,a12,i4,a36')
a, arr, b = unpackRecord(line, 1, 'i4,3i4,i4')

The result is obviously not idiomatic Python, but it is much easier to compare the Python to the original Fortran code.

This function only supports a small subset of the Fortran format strings. Basically you can use:

aN, iN

A string or integer in a field width of N. For example ‘i5, s20’.

MiN

An array of M intgers, each in an N character field. The returned value is a list of integers.

Note: This is throw-away code, which does very little error checking.

Return Value

A tuple of values, where each entry corresponds to a value decoded using the rules defined in the format argument. Where the format argument indicates an array of values, the tuple entry is itself a tuple.

Arguments

line

The line of text to be ‘unpacked’.

start

The start character in line to read from. Fortran indexing is used; i.e. the first character is as position 1.

format

The format string. This follows the Fortran conventions, but without the parentheses.

Exceptions

class Error(...)

Base class for exceptions.

class FileFormatError(...)

Raised when an error in the format of a binary file is detected.

For example, each record in a Fortram unformatted file should start and end with the same record length value. A record where the leading and trailing lengths do not match is a situation that will cause this error to be raised.

class FileTruncatedError(...)

Raised when there are unsufficent bytes in the file.

This can occur if, for example, a record header indicates that the next record (plus trailer) requires more bytes than remain to be read from the file.