Compile Fortran module with f2py

Question

I have a Fortran module which I am trying to compile with f2py (listed below). When I remove the module declaration and leave the subroutine in the file by itself, everything works fine. However, if the module is declared as shown below, I get the following results:

> f2py.py -c -m its --compiler=mingw itimes-s2.f
...
Reading fortran codes...
    Reading file 'itimes-s2.f' (format:fix,strict)
crackline: groupcounter=1 groupname={0: '', 1: 'module', 2: 'interface', 3: 'subroutine'}
crackline: Mismatch of blocks encountered. Trying to fix it by assuming "end" statement.
...
c:\users\astay13\appdata\local\temp\tmpgh5ag8\Release\users\astay13\appdata\local\temp\tmpgh5ag8\src.win32-3.2\itsmodule.o:itsmodule.c:(.data+0xec): undefined reference to `itimes_'
collect2: ld returned 1 exit status

What is different about compiling a module or subroutine in f2py? Have I left something important out in the module that causes f2py to have trouble? Note that the module compiles fine when I use gfortran alone.

Software: Windows 7; gcc, gfortran 4.6.1 (MinGW); python 3.2.2; f2py v2

itimes-s2.f:

  module its

  contains

  subroutine itimes(infile,outfile)

    implicit none

    ! Constants
    integer, parameter :: dp = selected_real_kind(15)

    ! Subroutine Inputs
    character(*), intent(in) :: infile
    character(*), intent(in) :: outfile

    ! Internal variables
    real(dp) :: num
    integer :: inu
    integer :: outu
    integer :: ios

    inu = 11
    outu = 22

    open(inu,file=infile,action='read')
    open(outu,file=outfile,action='write',access='append')

    do
      read(inu,*,IOSTAT=ios) num
      if (ios < 0) exit

      write(outu,*) num**2
    end do

  end subroutine itimes

  end module its

Answer 1

You are trying to have a Fortran module in a Python module. If you want that, the names must be different, e.g.

 f2py.py -c -m SOMEDIFFERENTNAME itimes-s2.f

The result will be called as pythonmodule.fortranmodule.yourfunction().

You can also import it as

from pythonmodule import fortranmodule
fortranmodule.yourfunction()

Otherwise it worked on my machine.

Answer 2

For f2py to work you need to have a signature file to direct the interface creation or modify your source code with f2py comments to help with the interface. See http://cens.ioc.ee/projects/f2py2e/usersguide/#signature-file for more information.

From that site:

C FILE: FIB3.F
      SUBROUTINE FIB(A,N)
C
C     CALCULATE FIRST N FIBONACCI NUMBERS
C
      INTEGER N
      REAL*8 A(N)
Cf2py intent(in) n
Cf2py intent(out) a
Cf2py depend(n) a
      DO I=1,N
         IF (I.EQ.1) THEN
            A(I) = 0.0D0
         ELSEIF (I.EQ.2) THEN
            A(I) = 1.0D0
         ELSE 
            A(I) = A(I-1) + A(I-2)
         ENDIF
      ENDDO
      END
C END FILE FIB3.F

Building the extension module can be now carried out in one command:

f2py -c -m fib3 fib3.f