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      1 # This file must use Python 1.5 syntax.
      2 import glob
      3 import os
      4 import re
      5 import string
      6 import sys
      7 
      8 
      9 class check_python_version:
     10 
     11     def __init__(self):
     12         version = None
     13         try:
     14             version = sys.version_info[0:2]
     15         except AttributeError:
     16             pass # pre 2.0, no neat way to get the exact number
     17 
     18         # The change to prefer 2.4 really messes up any systems which have both
     19         # the new and old version of Python, but where the newer is default.
     20         # This is because packages, libraries, etc are all installed into the
     21         # new one by default. Some things (like running under mod_python) just
     22         # plain don't handle python restarting properly. I know that I do some
     23         # development under ipython and whenever I run (or do anything that
     24         # runs) 'import common' it restarts my shell. Overall, the change was
     25         # fairly annoying for me (and I can't get around having 2.4 and 2.5
     26         # installed with 2.5 being default).
     27         if not version or version < (2, 4) or version >= (3, 0):
     28             try:
     29                 # We can't restart when running under mod_python.
     30                 from mod_python import apache
     31             except ImportError:
     32                 self.restart()
     33 
     34 
     35     def extract_version(self, path):
     36         match = re.search(r'/python(\d+)\.(\d+)$', path)
     37         if match:
     38             return (int(match.group(1)), int(match.group(2)))
     39         else:
     40             return None
     41 
     42 
     43     PYTHON_BIN_GLOB_STRINGS = ['/usr/bin/python2*', '/usr/local/bin/python2*']
     44 
     45 
     46     def find_desired_python(self):
     47         """Returns the path of the desired python interpreter."""
     48         pythons = []
     49         for glob_str in self.PYTHON_BIN_GLOB_STRINGS:
     50             pythons.extend(glob.glob(glob_str))
     51 
     52         possible_versions = []
     53         best_python = (0, 0), ''
     54         for python in pythons:
     55             version = self.extract_version(python)
     56             if version >= (2, 4):
     57                 possible_versions.append((version, python))
     58 
     59         possible_versions.sort()
     60 
     61         if not possible_versions:
     62             raise ValueError('Python 2.x version 2.4 or better is required')
     63         # Return the lowest possible version so that we use 2.4 if available
     64         # rather than more recent versions.
     65         return possible_versions[0][1]
     66 
     67 
     68     def restart(self):
     69         python = self.find_desired_python()
     70         sys.stderr.write('NOTE: %s switching to %s\n' %
     71                          (os.path.basename(sys.argv[0]), python))
     72         sys.argv.insert(0, '-u')
     73         sys.argv.insert(0, python)
     74         os.execv(sys.argv[0], sys.argv)
     75