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# (C) Copyright 2005-2025 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
""" A Python based configuration file with hierarchical sections. """
class PyConfigFile(dict):
""" A Python based configuration file with hierarchical sections. """
###########################################################################
# 'object' interface.
###########################################################################
def __init__(self, file_or_filename=None):
"""Constructor.
If 'file_or_filename' is specified it will be loaded immediately. It
can be either:-
a) a filename
b) a file-like object that must be open for reading
"""
# A dictionary containing one namespace instance for each root of the
# config hierarchy (see the '_Namespace' class for more details).
#
# e.g. If the following sections have been loaded:-
#
# [acme.foo]
# ...
# [acme.bar]
# ...
# [tds]
# ...
# [tds.baz]
# ...
#
# Then the dictionary will contain:-
#
# {'acme' : <A _Namespace instance>, 'tds' : <A _Namespace instance>}
#
self._namespaces = {}
if file_or_filename is not None:
self.load(file_or_filename)
###########################################################################
# 'PyConfigFile' interface.
###########################################################################
def load(self, file_or_filename):
"""Load the configuration from a file.
'file_or_filename' can be either:-
a) a filename
b) a file-like object that must be open for reading
"""
# Get an open file to read from.
f = self._get_file(file_or_filename)
section_name = None
section_body = ""
for line in f:
stripped = line.strip()
# Is this line a section header?
#
# If so then parse the preceding section (if there is one) and
# start collecting the body of the new section.
if stripped.startswith("[") and stripped.endswith("]"):
if section_name is not None:
self._parse_section(section_name, section_body)
section_name = stripped[1:-1]
section_body = ""
# Otherwise, this is *not* a section header so add the line to the
# body of the current section. If there is no current section then
# we simply ignore it!
else:
if section_name is not None:
section_body += line
# Parse the last section in the file.
if section_name is not None:
self._parse_section(section_name, section_body)
f.close()
def save(self, file_or_filename):
"""Save the configuration to a file.
'file_or_filename' can be either:-
a) a filename
b) a file-like object that must be open for writing
"""
f = self._get_file(file_or_filename, "w")
for section_name, section_data in self.items():
self._write_section(f, section_name, section_data)
f.close()
###########################################################################
# Private interface.
###########################################################################
def _get_file(self, file_or_filename, mode="r"):
"""Return an open file object from a file or a filename.
The mode is only used if a filename is specified.
"""
if isinstance(file_or_filename, str):
f = open(file_or_filename, mode)
else:
f = file_or_filename
return f
def _get_namespace(self, section_name):
""" Return the namespace that represents the section. """
components = section_name.split(".")
namespace = self._namespaces.setdefault(components[0], _Namespace())
for component in components[1:]:
namespace = getattr(namespace, component)
return namespace
def _parse_section(self, section_name, section_body):
"""Parse a section.
In this implementation, we don't actually 'parse' anything - we just
execute the body of the section as Python code ;^)
"""
# If this is the first time that we have come across the section then
# start with an empty dictionary for its contents. Otherwise, we will
# update its existing contents.
section = self.setdefault(section_name, {})
# Execute the Python code in the section dictionary.
#
# We use 'self._namespaces' as the globals for the code execution so
# that config values can refer to other config values using familiar
# Python syntax (see the '_Namespace' class for more details).
#
# e.g.
#
# [acme.foo]
# bar = 1
# baz = 99
#
# [acme.blargle]
# blitzel = acme.foo.bar + acme.foo.baz
exec(section_body, self._namespaces, section)
# The '__builtins__' dictionary gets added to 'self._namespaces' as
# by the call to 'exec'. However, we want 'self._namespaces' to only
# contain '_Namespace' instances, so we do the cleanup here.
del self._namespaces["__builtins__"]
# Get the section's corresponding node in the 'dotted' namespace and
# update it with the config values.
namespace = self._get_namespace(section_name)
namespace.__dict__.update(section)
def _write_section(self, f, section_name, section_data):
""" Write a section to a file. """
f.write("[%s]\n" % section_name)
for name, value in section_data.items():
f.write("%s = %s\n" % (name, repr(value)))
f.write("\n")
###########################################################################
# Debugging interface.
###########################################################################
def _pretty_print_namespaces(self):
""" Pretty print the 'dotted' namespaces. """
for name, value in self._namespaces.items():
print("Namespace:", name)
value.pretty_print(" ")
###############################################################################
# Internal use only.
###############################################################################
class _Namespace(object):
"""An object that represents a node in a dotted namespace.
We build up a dotted namespace so that config values can refer to other
config values using familiar Python syntax.
e.g.
[acme.foo]
bar = 1
baz = 99
[acme.blargle]
blitzel = acme.foo.bar + acme.foo.baz
"""
###########################################################################
# 'object' interface.
###########################################################################
def __getattr__(self, name):
""" Return the attribute with the specified name. """
# This looks a little weird, but we are simply creating the next level
# in the namespace hierarchy 'on-demand'.
namespace = self.__dict__[name] = _Namespace()
return namespace
###########################################################################
# Debugging interface.
###########################################################################
def pretty_print(self, indent=""):
""" Pretty print the namespace. """
for name, value in self.__dict__.items():
if isinstance(value, _Namespace):
print(indent, "Namespace:", name)
value.pretty_print(indent + " ")
else:
print(indent, name, ":", value)
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