Compatibility with old OS Python versions (specifically 2.4 in RHE5!).

1 files changed, 38 insertions, 30 deletions

diff --git a/scripts/ac_update_extern_pkg b/scripts/ac_update_extern_pkg
index 51905da..ec033dd 100644
--- a/scripts/ac_update_extern_pkg
+++ b/scripts/ac_update_extern_pkg
@@ -5,12 +5,14 @@
 # in progress when it gets run. It is not made executable because conda insists
 # on changing any Python interpreter path to $PREFIX/bin/python, which does not
 # always exist; it can instead be invoked via ac_config_iraf_pkg.
+#
+# Supporting ancient OS Python versions (v2.4 in RHE 5) means avoiding features
+# such as argparse, new-style string formatting, context managers etc.
 
-import argparse
+import sys
 import os, os.path
 import shutil
 import re
-from collections import OrderedDict
 
 
 # AstroConda naming conventions:
@@ -22,37 +24,41 @@ path_sub      = 'UR_VDIR'            # a regexp
 
 
 # Get command-line user arguments:
-parser = argparse.ArgumentParser()
+usage = """
+Usage: ac_update_extern_pkg path name
 
-parser.add_argument('path', type=str,
-                    help='path to {0} and {1}/'.format(extern_pkg, extern_dir))
+positional arguments:
+  path        directory containing extern.pkg and iraf_extern/
+  name        name of IRAF package (and its directory)
+"""
+if len(sys.argv) != 3:
+    sys.exit(usage)
+args_path, args_name = sys.argv[1:]
 
-parser.add_argument('name', type=str,
-                    help='name of IRAF package (and its directory)')
-
-args = parser.parse_args()
 
 # Convert to canonical path and ensure it exists, with an extern.pkg file and
 # an iraf_extern/package/ur_extern.pkg (ie. files already installed):
-path = os.path.abspath(args.path)                     # env dir with extern.pkg
+path = os.path.abspath(args_path)                     # env dir with extern.pkg
 extpkg_path = os.path.join(path, extern_pkg)          # extern.pkg path
 extbak_path = os.path.join(path, extpkg_bak)          # path to backup copy
-pkg_path = os.path.join(path, extern_dir, args.name)  # path to this IRAF pkg
+pkg_path = os.path.join(path, extern_dir, args_name)  # path to this IRAF pkg
 template_path = os.path.join(pkg_path, template)      # this ur_extern.pkg
 
 if not os.access(extpkg_path, os.R_OK | os.W_OK):
-    raise ValueError("cannot access {0}".format(extpkg_path))
+    raise ValueError("cannot access %s" % (extpkg_path))
 
 if not os.access(template_path, os.R_OK):
-    raise ValueError("cannot access {0}".format(template_path))
+    raise ValueError("cannot access %s" % (template_path))
 
 # Read extern.pkg:
-with open(extpkg_path, 'r+') as extpkg_file:
-    buffer = extpkg_file.read()
+extpkg_file = open(extpkg_path, 'r+')
+buffer = extpkg_file.read()
+extpkg_file.close()
 
 # Read the package's template ur_extern.pkg, removing any outer blank lines:
-with open(template_path, 'r') as template_file:
-    tempbuf = template_file.read().strip()
+template_file = open(template_path, 'r')
+tempbuf = template_file.read().strip()
+template_file.close()
 
 # Here we convert the template entry to a regex for finding and removing old,
 # previously-generated entries for the same package. This mainly consists of
@@ -63,7 +69,7 @@ with open(template_path, 'r') as template_file:
 # because it's easier & more understandable to do those subs in concert with
 # the others. The template ur_extern.pkg files must not contain backslashes.
 
-replacements = OrderedDict((
+replacements = (
     ('special_nospace', (r'([][.^${}\|*?])',       r'\\\1')),
     ('special_sp_end',  (r'[ \t]*([=+()])[ \t]*$', r'[ \t]*\\\1')),
     ('special_space',   (r'[ \t]*([=+()])[ \t]*',  r'[ \t]*\\\1[ \t]*')),
@@ -72,7 +78,8 @@ replacements = OrderedDict((
     ('extra_space',     (r'[ \t]+',                r'[ \t]+')),
     ('line_space',      (r'\s*\n\s*',              r'\s*\n\s*')),  # see below
     ('path_sub',        (path_sub,                 r'.*')),
-))
+)
+repdict = dict(replacements) # keep both because no OrderedDict in python < 2.7
 
 # Note that ^ and $ only match in conjunction with their adjoining character,
 # which, unlike the \n above, can get consumed by a prior pattern. Also,
@@ -81,17 +88,17 @@ replacements = OrderedDict((
 
 # Concatenate individual expressions for replacement, so they can be done
 # simultaneously on the original buffer (otherwise they trip each other up):
-cat_re = '|'.join(['(?P<{0}>{1})'.format(key, regex) \
-                   for key, (regex, sub) in replacements.items()]) # py 3 way
+cat_re = '|'.join(['(?P<%s>%s)' % (key, regex) \
+                   for key, (regex, sub) in replacements])
 
 # Determine the replacement for a given match to the concatenated regex:
 def match_fn(match):
-    sub_re, sub = replacements[match.lastgroup]  # look up replacement tuple
+    sub_re, sub = repdict[match.lastgroup]       # look up replacement tuple
     return re.sub(sub_re, sub, match.group())    # do & return the substitution
 
 # Perform the substitutions to turn the template string into a regex itself:
 # template_re = re.escape(tempbuf) # if using built-in escape for special chars
-template_re = re.sub(cat_re, match_fn, tempbuf, flags=re.M)
+template_re = re.compile(cat_re, flags=re.M).sub(match_fn, tempbuf)
 
 # Update the original template entry with our new path:
 tempbuf = re.sub(path_sub, os.path.join(pkg_path, ''), tempbuf)  # trailing /
@@ -109,7 +116,7 @@ if match:
     buffer = buffer[:match.start()]
 
 # Make sure that what goes before the "keep" ends with a new line:
-buffer = re.sub('\n?\Z', '\n', buffer, flags=re.M)
+buffer = re.compile('\n?\Z', flags=re.M).sub('\n', buffer)
 
 # Find the last entry in extern.pkg (if any) that matches the template:
 match = None
@@ -129,15 +136,15 @@ if match:
     
     # Match any non-commented instances of the package name, in the remainder
     # of the buffer, that don't look like a substring of a longer name:
-    pkgname_re = '^[^\n#]*(?<![A-z0-9_-]){0}(?![A-z0-9_-])'.format(args.name)
+    pkgname_re = '^[^\n#]*(?<![A-z0-9_-])%s(?![A-z0-9_-])' % (args_name)
     later_match = re.search(pkgname_re, buffer[match.end():], flags=re.M)
 
     # Where a later (user) definition is found, we still remove the last
     # template-based definition but then continue as if there had been no
     # match, so a new definition will get placed at the end of the file below:
     if later_match:
-        buffer = '{0}\n\n{1}'.format(buffer[:match.start()].rstrip(),
-                                     buffer[match.end():].lstrip())
+        buffer = '%s\n\n%s' % (buffer[:match.start()].rstrip(),
+                               buffer[match.end():].lstrip())
         match = None
 
 # Replace the applicable entry with the template-based version:
@@ -147,7 +154,7 @@ if match:
 # If there wasn't an existing entry, or the last one wasn't based on the
 # template, put the new entry at the end:
 else:
-    buffer += '{0}\n\n'.format(tempbuf)
+    buffer += '%s\n\n' % tempbuf
 
 # Restore the "keep" line at the end (along with a semicolon to avoid an IRAF
 # parser bug when the last entry ends with a curly bracket):
@@ -158,8 +165,9 @@ os.rename(extpkg_path, extbak_path)
 
 # Write the modified extern.pkg as a new file with the same name, otherwise
 # conda's hard linking propagates its changes to other environments!:
-with open(extpkg_path, 'w') as extpkg_file:
-    extpkg_file.write(buffer)
+extpkg_file = open(extpkg_path, 'w')
+extpkg_file.write(buffer)
+extpkg_file.close()
 
 # Inherit permissions from the original copy (just as good practice):
 shutil.copymode(extbak_path, extpkg_path)