#
##
## This file is part of pyFormex 2.0 (Mon Sep 14 12:29:05 CEST 2020)
## pyFormex is a tool for generating, manipulating and transforming 3D
## geometrical models by sequences of mathematical operations.
## Home page: http://pyformex.org
## Project page: http://savannah.nongnu.org/projects/pyformex/
## Copyright 2004-2020 (C) Benedict Verhegghe (benedict.verhegghe@ugent.be)
## Distributed under the GNU General Public License version 3 or later.
##
## This program is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program. If not, see http://www.gnu.org/licenses/.
##
"""A general yet simple configuration class.
| (C) 2005, 2019 Benedict Verhegghe
| Distributed under the GNU GPL version 3 or later
Why
I wrote this simple class because I wanted to use Python
expressions in my configuration files. This is so much more fun
than using .INI style config files. While there are some other
Python config modules available on the web, I couldn't find one
that suited my needs and my taste: either they are intended for
more complex configuration needs than mine, or they do not work
with the simple Python syntax I expected.
What
Our Config class is just a normal Python dictionary which can hold
anything. Fields can be accessed either as dictionary lookup
(config['foo']) or as object attributes (config.foo). The class
provides a function for reading the dictionary from a flat text
(multiline string or file). I will always use the word 'file'
hereafter, because that is what you usually will read the
configuration from. Your configuration file can have named
sections. Sections are stored as other Python dicts inside the top
Config dictionary. The current version is limited to one level of
sectioning.
"""
from pyformex.mydict import Dict
from pyformex import Path
[docs]class Config(Dict):
"""A configuration class allowing Python expressions in the input.
The Config class is a subclass of the :class:`Dict` mapping, which
provides access to items by either dict-style key lookup
``config['foo']``, attribute syntax ``config.foo`` or call syntax
``config('foo')``. Furthermore, the Dict class allows a default_factory
function to lookup in another Dict. This allows a chain of Config
objects: session_prefs -> user_prefs -> factory_defaults.
The Config class is different from its parent Dict class in two ways:
- Keys should only be strings that are valid Python variable names,
except that they can also contain a '/' character.
The '/' splits up the key in two parts: the first part becomes a
key in the Config, and its value is a dict where the values are stored
with the second part of the key. This allows for creating sections
in the configuration. Currently only one level of sectioning is
allowed (keys can obnly have a single '/' character.
- A Config instance can be initialized or updated with a text in
Python source style. This provides an easy way to store
configurations in files with Python style. The Config class also
provides a way to export its contents to such a Python source text:
updated configurations can thus be written back to a configuration
file. See Notes below for details.
Parameters
----------
data: dict or multiline string, optional
Data to initialize the Config. If a dict, all keys should follow
the rules for valid config keys formulated above.
If a multiline string, it should be an executable Python source
text, with the limitations and exceptions outlined in the Notes
below.
default: :class:`Config` object, optional
If provided, this object will be used as default lookup for
missing keys.
Notes
-----
The configuration object can be initialized from a dict or from
a multiline string. Using a dict is obvious: one only has to obey
the restriction that keys should be valid Python variable names.
The format of the multiline config text is described hereafter.
This is also the format in which config files are written and
can be loaded.
All config lines should have the format: key = value, where key is a
string and value is a Python expression The first '=' character on the
line is the delimiter between key and value. Blanks around both the
key and the value are stripped. The value is then evaluated as a
Python expression and stored in a variable with name specified by the
key. This variable is available for use in subsequent configuration
lines. It is an error to use a variable before it is defined. The
key,value pair is also stored in the Config dictionary, unless the key
starts with an underscore ('_'): this provides for local variables.
Lines starting with '#' are comments and are ignored, as are empty
and blank lines. Lines ending with '\' are continued on the next
line. A line starting with '[' starts a new section. A section is
nothing more than a Python dictionary inside the Config
dictionary. The section name is delimited by '['and ']'. All
subsequent lines will be stored in the section dictionary instead
of the toplevel dictionary.
All other lines are executed as Python statements. This allows
e.g. for importing modules.
Whole dictionaries can be inserted at once in the Config with the
update() function.
All defined variables while reading config files remain available
for use in the config file statements, even over multiple calls to
the read() function. Variables inserted with addSection() will not
be available as individual variables though, but can be accessed as
``self['name']``.
As far as the resulting Config contents is concerned, the following are
equivalent::
C.update({'key':'value'})
C.read("key='value'\\n")
There is an important difference though: the second line will make a
variable key (with value 'value') available in subsequent Config read()
method calls.
Examples
--------
>>> C = Config('''# A simple config example
... aa = 'bb'
... bb = aa
... [cc]
... aa = 'aa' # yes ! comments are allowed)
... _n = 3 # local: will get stripped
... rng = list(range(_n))
... ''')
>>> C
Config({'aa': 'bb', 'bb': 'bb', 'cc': Dict({'aa': 'aa', 'rng': [0, 1, 2]})})
>>> C['aa']
'bb'
>>> C['cc']
Dict({'aa': 'aa', 'rng': [0, 1, 2]})
>>> C['cc/aa']
'aa'
Create a new Config with default lookup in C
>>> D = Config(default=C)
>>> D
Config({})
>>> D['aa'] # Get from C
'bb'
>>> D['cc'] # Get from C
Dict({'aa': 'aa', 'rng': [0, 1, 2]})
>>> D['cc/aa'] # Get from C
'aa'
>>> D.get('cc/aa','zorro') # but get method does not cascade!
'zorro'
Setting values in D will store them in D while C remains unchanged.
>>> D['aa'] = 'wel'
>>> D['dd'] = 'hoe'
>>> D['cc/aa'] = 'ziedewel'
>>> D
Config({'aa': 'wel', 'dd': 'hoe', 'cc': Dict({'aa': 'ziedewel'})})
>>> C
Config({'aa': 'bb', 'bb': 'bb', 'cc': Dict({'aa': 'aa', 'rng': [0, 1, 2]})})
>>> D['cc/aa']
'ziedewel'
>>> D['cc']
Dict({'aa': 'ziedewel'})
>>> D['cc/rng']
[0, 1, 2]
>>> 'ee' in D
False
>>> 'cc/ee' in D
False
>>> D['cc/bb'] = 'ok'
>>> list(D.keys())
['aa', 'dd', 'cc', 'cc/aa', 'cc/bb']
>>> del D['aa']
>>> del D['cc/aa']
>>> list(D.keys())
['dd', 'cc', 'cc/bb']
>>> del D['cc']
>>> list(D.keys())
['dd']
"""
_filename = None
def __init__(self, data={}, default=Dict.returnNone):
"""Creates a new Config instance.
The configuration can be initialized with a dictionary, or
with a variable that can be passed to the read() function.
The latter includes the name of a config file, or a multiline string
holding the contents of a configuration file.
"""
Dict.__init__(self, default_factory=default)
if isinstance(data, dict):
self.update(data)
elif data:
self.read(data)
Config._filename = None
[docs] def update(self, data={}, name=None, removeLocals=False):
"""Add a dictionary to the Config object.
The data, if specified, should be a valid Python dict.
If no name is specified, the data are added to the top dictionary
and will become attributes.
If a name is specified, the data are added to the named attribute,
which should be a dictionary. If the name does not specify a
dictionary, an empty one is created, deleting the existing attribute.
If a name is specified, but no data, the effect is to add a new
empty dictionary (section) with that name.
If removeLocals is set, keys starting with '_' are removed from the
data before updating the dictionary and not
included in the config. This behaviour can be changed by setting
removeLocals to false.
"""
if removeLocals:
for k in list(data.keys()):
if k[0] == '_':
del data[k]
if name:
if name not in self or not isinstance(self[name], dict):
self[name] = Dict()
self[name].update(data)
else:
Dict.update(self, data)
def _read_error(self, lineno, line):
if self._filename:
where = 'config file %s,' % Config._filename
else:
where = ''
raise RuntimeError('Error in %s line %d:\n%s' % (where, lineno, line))
[docs] def load(self, filename, debug=False):
"""Read a configuration from a file in Config format.
Parameters
----------
filename: :term:`path_like`
Path of a text file in Config format.
Returns
-------
Config
Returns the Config self, update with the settings read from
the specified file.
"""
Config._filename = Path(filename)
with Config._filename.open('r') as fil:
self.read(fil, debug=debug)
Config._filename = None
return self
[docs] def read(self, txt, debug=False): # noqa: C901
"""Read a configuration from a file or text
`txt` is a sequence of strings. Any type that allows a loop like
``for line in txt:``
to iterate over its text lines will do. This could be an open file, or
a multiline text after splitting on '\\n'.
The function will try to react intelligently if a string is passed as
argument. If the string contains at least one '\\n', it will be
interpreted as a multiline string and be splitted on '\\n'.
Else, the string will be considered and a file with that name will
be opened. It is an error if the file does not exist or can not be
opened.
The function returns self, so that you can write: cfg = Config().
"""
if isinstance(txt, str) and '\n' in txt:
# It is a multiline string: config text
# Convert to list of strings
Config._filename = None
txt = txt.split('\n')
else:
# It is an open file or list of strings
pass
globals().update(self)
section = None
contents = {}
lineno = 0
continuation = False
comments = False
for line in txt:
lineno += 1
ls = line.strip()
if comments:
comments = ls[-3:] != '"""'
ls = ''
else:
comments = ls[:3] == '"""'
if comments or len(ls)==0 or ls[0] == '#':
continue
if continuation:
s += ls # noqa: F821
else:
s = ls
continuation = s[-1] == '\\'
if s[-1] == '\\':
s = s[:-1]
if continuation:
continue
if s[0] == '[':
if contents:
self.update(name=section, data=contents, removeLocals=True)
contents = {}
i = s.find(']')
if i<0:
self.read_error(lineno, line)
section = s[1:i]
if debug:
print("Starting new section '%s'" % section)
continue
else:
if debug:
print("READ: "+line)
i = s.find('=')
if i >= 0:
key = s[:i].strip()
if len(key) == 0:
self.read_error(lineno, line)
contents[key] = eval(s[i+1:].strip())
globals().update(contents)
else:
exec(s)
if contents:
self.update(name=section, data=contents, removeLocals=True)
return self
def __setitem__(self, key, val):
"""Allows items to be set as self[section/key] = val.
"""
i = key.rfind('/')
if i == -1:
self.update({key: val})
else:
self.update({key[i+1:]: val}, key[:i])
def __getitem__(self, key):
"""Allows items to be addressed as self[key].
This is equivalent to the Dict lookup, except that items in
subsections can also be retrieved with a single key of the format
section/key.
While this lookup mechanism works for nested subsections, the syntax
for config files allows for only one level of sections!
Also beware that because of this functions, no '/' should be used
inside normal keys and sections names.
"""
i = key.rfind('/')
if i == -1:
return Dict.__getitem__(self, key)
else:
try:
return self[key[:i]][key[i+1:]]
except KeyError:
return self.__missing__(key)
def __delitem__(self, key):
"""Allows items to be deleted with del self[section/key].
"""
i = key.rfind('/')
if i == -1:
if key in self:
Dict.__delitem__(self, key)
else:
try:
del self[key[:i]][key[i+1:]]
except Exception:
pass
def __str__(self):
"""Format the Config in a way that can be read back.
This function is mostly used to format the data for writing it to
a configuration file. See the write() method.
The return value is a multiline string with Python statements that can
be read back through Python to recreate the Config data. Usually
this is done with the Config.read() method.
"""
from pyformex.utils import formatDict
s = ''
for k, v in self.items():
if not isinstance(v, Dict):
s += formatDict({k: v})
for k, v in self.items():
if isinstance(v, Dict):
s += "\n[%s]\n" % k
s += formatDict(v)
return s
[docs] def write(self, filename,
header="# Config written by pyFormex -*- PYTHON -*-\n\n",
trailer="\n# End of config\n"):
"""Write the config to the given file
The configuration data will be written to the file with the given name
in a text format that is both readable by humans and by the
Config.read() method.
The header and trailer arguments are strings that will be added at
the start and end of the outputfile. Make sure they are valid
Python statements (or comments) and that they contain the needed
line separators, if you want to be able to read it back.
"""
filename = Path(filename)
with filename.open('w') as fil:
fil.write(header)
fil.write("%s" % self)
fil.write(trailer)
return filename
[docs] def keys(self, descend=True):
"""Return the keys in the config.
By default this descends one level of Dicts.
"""
keys = list(Dict.keys(self))
if descend:
for k, v in self.items():
if isinstance(v, Dict):
keys += ['%s/%s' % (k, ki) for ki in v]
return keys
if __name__ == '__main__':
import doctest
doctest.testmod()
# End
