Speedup sysconfig startup

Lib/sysconfig.py

 """Access to Python's configuration information."""
-
 import os
 import re
 import sys
 from os.path import pardir, realpath
-from configparser import RawConfigParser
 
 __all__ = [
     'get_config_h_filename',
     'get_config_var',
     'get_config_vars',
     'get_makefile_filename',
     'get_path',
     'get_path_names',
     'get_paths',
     'get_platform',
     'get_python_version',
     'get_scheme_names',
     'parse_config_h',
 ]
+
+class SectionProxy:
+    def __init__(self, parser, name):
+        self._parser = parser
+        self._name = name
+
+    def __iter__(self):
+        return iter(self._parser.options(self._name))
+
+class _ConfigParser:
+    """
+    configparser.RawConfigParser copy specialized for sysconfig:
+     - read-only
+     - use dict
+     - only support "#" prefix for comments
+     - only support "=" option name/value separator
+     - don't use custom exceptions
+    """
+
+    def __init__(self):
+        self._sections = dict()
+        self._proxies = dict()
+
+    def sections(self):
+        return list(self._sections.keys())
+
+    def add_section(self, section):
+        if section in self._sections:
+            raise Exception("Section %s already exists" % section)
+        self._sections[section] = dict()
+        self._proxies[section] = SectionProxy(self, section)
+
+    def has_section(self, section):
+        return section in self._sections
+
+    def options(self, section):
+        return list(self._sections[section].keys())
+
+    def items(self, section):
+        return self._sections[section].items()
+
+    def has_option(self, section, option):
+        if section not in self._sections:
+            return False
+        else:
+            option = option
+            return option in self._sections[section]
+
+    def set(self, section, option, value=None):
+        self._sections[section][option] = value
+
+    def remove_section(self, section):
+        existed = section in self._sections
+        if existed:
+            del self._sections[section]
+            del self._proxies[section]
+        return existed
+
+    def __getitem__(self, key):
+        return self._proxies[key]
+
+    def __iter__(self):
+        return iter(self._sections.keys())
+
+    def read(self, filename):
+        with open(filename, encoding="ASCII") as fp:
+            self._read(fp, filename)
+
+    def _read(self, fp, fpname):
+        cursect = None                        # None, or a dictionary
+        sectname = None
+        optname = None
+        lineno = 0
+        for lineno, line in enumerate(fp, start=1):
+            value = line.strip()
+            if value.startswith('#'):
+                continue
+            if not value:
+                continue
+
+            # is it a section header?
+            if value.startswith('[') and value.endswith(']'):
+                sectname = value[1:-1]
+                if sectname in self._sections:
+                    raise Exception("%s:%s: Section %s already exists"
+                                    % (fpname, lineno, sectname))
+                else:
+                    cursect = dict()
+                    self._sections[sectname] = cursect
+                    self._proxies[sectname] = SectionProxy(self, sectname)
+                # So sections can't start with a continuation line
+                optname = None
+            # no section header in the file?
+            elif cursect is None:
+                raise Exception('%s:%s: File contains no section headers'
+                                % (fpname, lineno))
+            # an option line?
+            else:
+                optname, optval = value.split('=', 1)
+                optname = optname.rstrip()
+                optval = optval.lstrip()

[gregory.p.smith, 2012/03/20 05:13:35]

do we need to preserve trailing spaces on a value?  if not, optval.strip().

[haypo, 2012/03/20 10:22:22]

line.strip() is supposed to have already removed trailing spaces. Am I wrong?

+                if not optname:
+                    raise ValueError("%s:%s: Empty option name"
+                                     % (fpname, lineno))
+                optname = optname.rstrip()

[gregory.p.smith, 2012/03/20 05:13:35]

you already did this above.

[haypo, 2012/03/20 10:22:22]

Ah yes, I forgot it in the cleanup.

+                if optname in cursect:
+                    raise DuplicateOptionError(sectname, optname,
+                                               fpname, lineno)
+                cursect[optname] = optval
 
 # let's read the configuration file
 # XXX _CONFIG_DIR will be set by the Makefile later
 _CONFIG_DIR = os.path.normpath(os.path.dirname(__file__))
 _CONFIG_FILE = os.path.join(_CONFIG_DIR, 'sysconfig.cfg')
-_SCHEMES = RawConfigParser(dict_type=dict)   # Faster than OrderedDict
+_SCHEMES = _ConfigParser()
 _SCHEMES.read(_CONFIG_FILE)
 _VAR_REPL = re.compile(r'\{([^{]*?)\}')
 
 
 def _expand_globals(config):
     if config.has_section('globals'):
         globals = config.items('globals')
     else:
         globals = tuple()
 
@@ skipping 739 matching lines @@
     print('Python version: "%s"' % get_python_version())
     print('Current installation scheme: "%s"' % _get_default_scheme())
     print()
     _print_dict('Paths', get_paths())
     print()
     _print_dict('Variables', get_config_vars())
 
 
 if __name__ == '__main__':
     _main()
+