User:Timothee Flutre/Notebook/Postdoc/2012/05/16

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Typical templates for Python scripts and C++ programs

It is always rewarding on the long term to start any piece of computer software with a minimum amount of generic code (verbose, command-line options, help message, license, etc). But it's a pain to write all this every time, right? So below are my typical templates for any Python script and C++ programs.

  • Python: it is assumed that the code below is copied into a file named "MyClass.py".
   #!/usr/bin/env python
   
   # Author: Timothee Flutre
   # License: GPL-3
   # Aim: does this and that
   # help2man -o MyClass.man ./MyClass.py
   # groff -mandoc MyClass.man > MyClass.ps
   
   import sys
   import os
   import getopt
   import time
   import datetime
   import math
   
   
   class MyClass(object):
       
       def __init__(self):
           self.verbose = 1
           self.input = ""
           
           
       def help(self):
           msg = "`%s' does this and that.\n" % os.path.basename(sys.argv[0])
           msg += "\n"
           msg += "Usage: %s [OPTIONS] ...\n" % os.path.basename(sys.argv[0])
           msg += "\n"
           msg += "Options:\n"
           msg += " -h, --help\tdisplay the help and exit\n"
           msg += " -V, --version\toutput version information and exit\n"
           msg += " -v, --verbose\tverbosity level (0/default=1/2/3)\n"
           msg += " -i\tinput"
           msg += "\n"
           msg += "Examples:\n"
           print msg; sys.stdout.flush()
           
           
       def version(self):
           msg = "%s 0.1\n" % os.path.basename(sys.argv[0])
           msg += "\n"
           msg += "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>\n"
           msg += "This is free software; see the source for copying conditions.  There is NO\n"
           msg += "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n"
           print msg; sys.stdout.flush()
           
           
       def setAttributesFromCmdLine(self):
           try:
               opts, args = getopt.getopt( sys.argv[1:], "hVv:i:",
                                           ["help", "version", "verbose="])
           except getopt.GetoptError, err:
               sys.stderr.write("%s\n" % str(err))
               self.help()
               sys.exit(2)
           for o, a in opts:
               if o in ("-h", "--help"):
                   self.help()
                   sys.exit(0)
               elif o in ("-V", "--version"):
                   self.version()
                   sys.exit(0)
               elif o in ("-v", "--verbose"):
                   self.verbose = int(a)
               elif o in ("-i"):
                    self.input = a
               else:
                   assert False, "unhandled option"
                   
                   
       def checkAttributes(self):
           if self.input == "":
               msg = "ERROR: missing required argument -i"
               sys.stderr.write("%s\n\n" % msg)
              self.help()
              sys.exit(1)
              
              
       def run(self):
           self.checkAttributes()
           
           if self.verbose > 0:
               msg = "START %s" % time.strftime("%Y-%m-%d %H:%M:%S")
               startTime = time.time()
               print msg; sys.stdout.flush()
               
           # ... specific code ...
           
           if self.verbose > 0:
               msg = "END %s" % time.strftime("%Y-%m-%d %H:%M:%S")
               endTime = time.time()
               runLength = datetime.timedelta(seconds=
                                              math.floor(endTime - startTime))
               msg += " (%s)" % str(runLength)
               print msg; sys.stdout.flush()
               
               
   if __name__ == "__main__":
       i = MyClass()
       i.setAttributesFromCmdLine()
       i.run()


  • C++: it is assumed that the code below is copied into a file named "myprogram.cpp" and that the file "utils.cpp" is present in the same directory.
/** \file myprogram.cpp
 *
 *  `myprogram' does this and that.
 *  Copyright (C) 2011,2012 Timothee Flutre
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  g++ -Wall -fopenmp -O3 myprogram.cpp -lgsl -lgslcblas -o myprogram
 *  help2man -o .man ./myprogram
 *  groff -mandoc myprogram.man > myprogram.ps
*/

#include <cmath>
#include <ctime>
#include <getopt.h>

#include <iostream>
#include <string>
using namespace std;

#include "utils.cpp"

/** \brief Display the help on stdout.
*/
void help (char ** argv)
{
  cout << "`" << argv[0] << "'"
       << " does this and that." << endl
       << endl
       << "Usage: " << argv[0] << " [OPTIONS] ..." << endl
       << endl
       << "Options:" << endl
       << "  -h, --help\tdisplay the help and exit" << endl
       << "  -V, --version\toutput version information and exit" << endl
       << "  -v, --verbose\tverbosity level (0/default=1/2/3)" << endl
       << "  -i, --in\tinput" << endl
       << endl
       << "Examples:" << endl
       << "  " << argv[0] << " -i <input>" << endl
       << endl
       << "Remarks:" << endl
       << "  This is my typical template file for C++." << endl
    ;
}

/** \brief Display version and license information on stdout.
 */
void version (char ** argv)
{
  cout << argv[0] << " 0.1" << endl
       << endl
       << "Copyright (C) 2011,2012 T. Flutre." << endl
       << "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>" << endl
       << "This is free software; see the source for copying conditions.  There is NO" << endl
       << "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE." << endl
       << endl
       << "Written by T. Flutre." << endl;
}

/** \brief Parse the command-line arguments and check the values of the 
 *  compulsory ones.
 */
void
parse_args (
  int argc,
  char ** argv,
  string & input,
  int & verbose)
{
  int c = 0;
  while (1)
  {
    static struct option long_options[] =
      {
        {"help", no_argument, 0, 'h'},
        {"version", no_argument, 0, 'V'},
        {"verbose", required_argument, 0, 'v'},
        {"input", required_argument, 0, 'i'},
        {0, 0, 0, 0}
      };
    int option_index = 0;
    c = getopt_long (argc, argv, "hVv:i:",
                     long_options, &option_index);
    if (c == -1)
      break;
    switch (c)
    {
    case 0:
      if (long_options[option_index].flag != 0)
        break;
    case 'h':
      help (argv);
      exit (0);
    case 'V':
      version (argv);
      exit (0);
    case 'v':
      verbose = atoi(optarg);
      break;
    case 'i':
      input = optarg;
      break;
    case '?':
      printf ("\n"); help (argv);
      abort ();
    default:
      printf ("\n"); help (argv);
      abort ();
    }
  }
  if (input.empty())
  {
    fprintf (stderr, "ERROR: missing input (-i).\n\n");
    help (argv);
    exit (1);
  }
  if (! doesFileExist (input))
  {
    fprintf (stderr, "ERROR: can't find file '%s'.\n\n", input.c_str());
    help (argv);
    exit (1);
  }
}

int main (int argc, char ** argv)
{
  string input;
  int verbose = 1;
  
  parse_args (argc, argv, input, verbose);
  
  time_t startRawTime, endRawTime;
  if (verbose > 0)
  {
    time (&startRawTime);
    cout << "START " << argv[0] << " (" << time2string (startRawTime) << ")"
         << endl;
  }
  
  // ... specific code ...
  
  if (verbose > 0)
  {
    time (&endRawTime);
    cout << "END " << argv[0] << " (" << time2string (endRawTime)
         << ": elapsed -> " << elapsedTime(startRawTime, endRawTime)
         << ")" << endl;
  }
  
  return EXIT_SUCCESS;
}


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