Sort the OPN most wanted roadblocks file

opnfiles.py

#! /usr/bin/env python3
# indent width: 5 spaces

# default sort method to use:
sortkey = lambda line: line.snfs_difficulty()

###############################################################################

from math import log10
from abc import ABCMeta, abstractmethod

class OPNLine(metaclass=ABCMeta):

     @abstractmethod
     def __init__(self, line):
          line = line.split()

          for i, section in enumerate(line):
               try:
                    line[i] = int(section)
               except ValueError:
                    raise ValueError("corrupt line, got piece {}".format(section))

          self.base, self.power, self.composite = line[:3]
          self._line = line


     def snfs_difficulty(self):
          '''Zeroth order estimate'''
          return log10(self.base) * self.power # log10 of (base^(power+1)-1)/(base-1)


     def gnfs_difficulty(self):
          return log10(self.composite)


     @property
     @abstractmethod
     def _str_template(self):
          pass


     def __str__(self):
          fmt, *args = self._str_template
          return fmt.format(*args)


class MostWantedLine(OPNLine):

     def __init__(self, line):
          super().__init__(line)
          self.weight = self._line[3]

     @property
     def _str_template(self):
          return ("{:.1f} {:.1f} {} {} {}\n", self.snfs_difficulty(), self.gnfs_difficulty(), self.weight, self.base, self.power)


class TLine(OPNLine):

     def __init__(self, line):
          return super().__init__(line)

     @property
     def _str_template(self):
          return ("{:.1f} {:.1f} {} {}\n", self.snfs_difficulty(), self.gnfs_difficulty(), self.base, self.power)


def determine_file_type(line):
     if len(line.split()) > 3:
          return MostWantedLine
     else:
          return TLine


def inner_main(file, _sortkey=None):
     lines = []
     if _sortkey is None: _sortkey = sortkey

     with open(file) as f:
          line = f.readline()
          OPNClass = determine_file_type(line) # t file or mwrb file?

          lines.append(OPNClass(line))
          for line in f:
               lines.append(OPNClass(line))

     lines.sort(key=_sortkey)

     with open(file+'.sort', 'w') as f:
          f.writelines(str(line) for line in lines)


def main(*argv):
     file = argv[1]
     sortkey = None
     if len(argv) > 2:
          sortkey = eval("lambda line: "+argv[2])
     inner_main(file, sortkey)


if __name__ == "__main__":
     from sys import argv
     main(*argv)