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# coding: utf-8
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"""A simple configuration system.
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Authors
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-------
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* Brian Granger
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* Fernando Perez
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"""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2008-2009 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import __builtin__
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import os
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import sys
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from IPython.external import argparse
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from IPython.utils.path import filefind
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#-----------------------------------------------------------------------------
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# Exceptions
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#-----------------------------------------------------------------------------
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class ConfigError(Exception):
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pass
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class ConfigLoaderError(ConfigError):
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pass
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#-----------------------------------------------------------------------------
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# Argparse fix
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#-----------------------------------------------------------------------------
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# Unfortunately argparse by default prints help messages to stderr instead of
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# stdout. This makes it annoying to capture long help screens at the command
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# line, since one must know how to pipe stderr, which many users don't know how
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# to do. So we override the print_help method with one that defaults to
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# stdout and use our class instead.
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class ArgumentParser(argparse.ArgumentParser):
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"""Simple argparse subclass that prints help to stdout by default."""
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def print_help(self, file=None):
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if file is None:
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file = sys.stdout
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return super(ArgumentParser, self).print_help(file)
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print_help.__doc__ = argparse.ArgumentParser.print_help.__doc__
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#-----------------------------------------------------------------------------
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# Config class for holding config information
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#-----------------------------------------------------------------------------
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class Config(dict):
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"""An attribute based dict that can do smart merges."""
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def __init__(self, *args, **kwds):
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dict.__init__(self, *args, **kwds)
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# This sets self.__dict__ = self, but it has to be done this way
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# because we are also overriding __setattr__.
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dict.__setattr__(self, '__dict__', self)
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def _merge(self, other):
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to_update = {}
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for k, v in other.items():
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if not self.has_key(k):
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to_update[k] = v
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else: # I have this key
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if isinstance(v, Config):
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# Recursively merge common sub Configs
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self[k]._merge(v)
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else:
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# Plain updates for non-Configs
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to_update[k] = v
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self.update(to_update)
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def _is_section_key(self, key):
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if key[0].upper()==key[0] and not key.startswith('_'):
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return True
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else:
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return False
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def has_key(self, key):
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if self._is_section_key(key):
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return True
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else:
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return dict.has_key(self, key)
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def _has_section(self, key):
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if self._is_section_key(key):
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if dict.has_key(self, key):
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return True
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return False
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def copy(self):
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return type(self)(dict.copy(self))
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def __copy__(self):
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return self.copy()
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def __deepcopy__(self, memo):
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import copy
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return type(self)(copy.deepcopy(self.items()))
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def __getitem__(self, key):
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# Because we use this for an exec namespace, we need to delegate
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# the lookup of names in __builtin__ to itself. This means
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# that you can't have section or attribute names that are
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# builtins.
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try:
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return getattr(__builtin__, key)
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except AttributeError:
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pass
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if self._is_section_key(key):
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try:
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return dict.__getitem__(self, key)
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except KeyError:
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c = Config()
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dict.__setitem__(self, key, c)
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return c
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else:
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return dict.__getitem__(self, key)
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def __setitem__(self, key, value):
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# Don't allow names in __builtin__ to be modified.
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if hasattr(__builtin__, key):
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raise ConfigError('Config variable names cannot have the same name '
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'as a Python builtin: %s' % key)
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if self._is_section_key(key):
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if not isinstance(value, Config):
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raise ValueError('values whose keys begin with an uppercase '
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'char must be Config instances: %r, %r' % (key, value))
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else:
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dict.__setitem__(self, key, value)
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def __getattr__(self, key):
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try:
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return self.__getitem__(key)
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except KeyError, e:
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raise AttributeError(e)
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def __setattr__(self, key, value):
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try:
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self.__setitem__(key, value)
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except KeyError, e:
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raise AttributeError(e)
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def __delattr__(self, key):
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try:
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dict.__delitem__(self, key)
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except KeyError, e:
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raise AttributeError(e)
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#-----------------------------------------------------------------------------
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# Config loading classes
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#-----------------------------------------------------------------------------
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class ConfigLoader(object):
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"""A object for loading configurations from just about anywhere.
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The resulting configuration is packaged as a :class:`Struct`.
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Notes
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-----
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A :class:`ConfigLoader` does one thing: load a config from a source
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(file, command line arguments) and returns the data as a :class:`Struct`.
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There are lots of things that :class:`ConfigLoader` does not do. It does
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not implement complex logic for finding config files. It does not handle
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default values or merge multiple configs. These things need to be
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handled elsewhere.
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"""
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def __init__(self):
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"""A base class for config loaders.
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Examples
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--------
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>>> cl = ConfigLoader()
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>>> config = cl.load_config()
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>>> config
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{}
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"""
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self.clear()
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def clear(self):
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self.config = Config()
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def load_config(self):
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"""Load a config from somewhere, return a :class:`Config` instance.
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Usually, this will cause self.config to be set and then returned.
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However, in most cases, :meth:`ConfigLoader.clear` should be called
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to erase any previous state.
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"""
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self.clear()
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return self.config
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class FileConfigLoader(ConfigLoader):
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"""A base class for file based configurations.
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As we add more file based config loaders, the common logic should go
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here.
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"""
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pass
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class PyFileConfigLoader(FileConfigLoader):
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"""A config loader for pure python files.
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This calls execfile on a plain python file and looks for attributes
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that are all caps. These attribute are added to the config Struct.
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"""
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def __init__(self, filename, path=None):
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"""Build a config loader for a filename and path.
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Parameters
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----------
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filename : str
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The file name of the config file.
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path : str, list, tuple
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The path to search for the config file on, or a sequence of
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paths to try in order.
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"""
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super(PyFileConfigLoader, self).__init__()
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self.filename = filename
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self.path = path
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self.full_filename = ''
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self.data = None
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def load_config(self):
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"""Load the config from a file and return it as a Struct."""
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self.clear()
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self._find_file()
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self._read_file_as_dict()
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self._convert_to_config()
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return self.config
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def _find_file(self):
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"""Try to find the file by searching the paths."""
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self.full_filename = filefind(self.filename, self.path)
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def _read_file_as_dict(self):
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"""Load the config file into self.config, with recursive loading."""
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# This closure is made available in the namespace that is used
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# to exec the config file. This allows users to call
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# load_subconfig('myconfig.py') to load config files recursively.
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# It needs to be a closure because it has references to self.path
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# and self.config. The sub-config is loaded with the same path
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# as the parent, but it uses an empty config which is then merged
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# with the parents.
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def load_subconfig(fname):
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loader = PyFileConfigLoader(fname, self.path)
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try:
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sub_config = loader.load_config()
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except IOError:
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# Pass silently if the sub config is not there. This happens
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# when a user us using a profile, but not the default config.
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pass
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else:
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self.config._merge(sub_config)
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# Again, this needs to be a closure and should be used in config
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# files to get the config being loaded.
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def get_config():
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return self.config
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namespace = dict(load_subconfig=load_subconfig, get_config=get_config)
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execfile(self.full_filename, namespace)
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def _convert_to_config(self):
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if self.data is None:
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ConfigLoaderError('self.data does not exist')
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class CommandLineConfigLoader(ConfigLoader):
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"""A config loader for command line arguments.
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As we add more command line based loaders, the common logic should go
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here.
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"""
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class ArgParseConfigLoader(CommandLineConfigLoader):
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def __init__(self, argv=None, *parser_args, **parser_kw):
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"""Create a config loader for use with argparse.
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Parameters
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----------
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argv : optional, list
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If given, used to read command-line arguments from, otherwise
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sys.argv[1:] is used.
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parser_args : tuple
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A tuple of positional arguments that will be passed to the
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constructor of :class:`argparse.ArgumentParser`.
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parser_kw : dict
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A tuple of keyword arguments that will be passed to the
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constructor of :class:`argparse.ArgumentParser`.
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"""
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super(CommandLineConfigLoader, self).__init__()
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if argv == None:
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argv = sys.argv[1:]
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self.argv = argv
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self.parser_args = parser_args
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kwargs = dict(argument_default=argparse.SUPPRESS)
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kwargs.update(parser_kw)
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self.parser_kw = kwargs
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def load_config(self, args=None):
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"""Parse command line arguments and return as a Struct.
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Parameters
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----------
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args : optional, list
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If given, a list with the structure of sys.argv[1:] to parse
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arguments from. If not given, the instance's self.argv attribute
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(given at construction time) is used."""
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self.clear()
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if args is None:
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args = self.argv
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self._create_parser()
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self._parse_args(args)
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self._convert_to_config()
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return self.config
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def get_extra_args(self):
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if hasattr(self, 'extra_args'):
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return self.extra_args
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else:
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return []
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def _create_parser(self):
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self.parser = ArgumentParser(*self.parser_args, **self.parser_kw)
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self._add_arguments()
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def _add_arguments(self):
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raise NotImplementedError("subclasses must implement _add_arguments")
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def _parse_args(self, args):
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"""self.parser->self.parsed_data"""
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self.parsed_data, self.extra_args = self.parser.parse_known_args(args)
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def _convert_to_config(self):
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"""self.parsed_data->self.config"""
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for k, v in vars(self.parsed_data).items():
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exec_str = 'self.config.' + k + '= v'
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exec exec_str in locals(), globals()
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