150 lines
3.9 KiB
Python
150 lines
3.9 KiB
Python
"""
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constant.Constants - The simple way to deal with environment constants.
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"""
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import os
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try:
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import ConfigParser as configparser
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except ImportError:
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import configparser
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import warnings
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import logging
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import functools
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logger = logging.getLogger(__name__)
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def debug(function):
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"""
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logging debug decorator
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"""
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@functools.wraps(function)
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def wrapper(*args, **kvargs):
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"""
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wrap method call
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"""
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logger.debug('begin %s %s',
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args,
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kvargs,
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extra={'method': function.__name__})
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result = function(*args, **kvargs)
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logger.debug('end %s', result, extra={'method': function.__name__})
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return result
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return wrapper
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VARIABLE = '__CONSTANTS__'
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FILENAME = 'constants.ini'
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class Constants(object):
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"""
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Environement sensitive application constants class
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"""
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@debug
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def __init__(self, variable=VARIABLE, filename=FILENAME):
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"""
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variable is the name of the environment variable to read the
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environment / config section from default to __CONSTANTS__
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filename is the config filename
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"""
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object.__setattr__(self, 'dict', {})
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self.variable = variable
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self.filename = filename
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self.load()
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@debug
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def load(self):
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"""
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load the section self.variable from the config file self.filename
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"""
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self.get_environment()
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self.read_config()
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self.load_dict()
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@debug
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def get_environment(self):
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"""
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returns the value of the environment variable self.variable
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"""
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self.environment = os.environ[self.variable]
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@debug
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def read_config(self):
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"""
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returns a ConfigParser instance from self.filename
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"""
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self.config = configparser.ConfigParser()
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with open(self.filename) as config_file:
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self.config.readfp(config_file)
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@debug
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def load_dict(self):
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"""
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load the config items into self.dict
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"""
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self.dict = dict (self.config.items(self.environment))
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logger.info('variable: %s, filename: %s, environment: %s, constants: %s',
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self.variable,
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self.filename,
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self.environment,
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self.dict,
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extra={'method': 'load'})
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@debug
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def __getitem__(self, item):
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"""
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access to environment specific constants in a dictionary manner
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casts to int, float or keep as string
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"""
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return self.cast(self.dict[item])
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@debug
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def __getattr__(self, item):
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"""
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syntactic sugar, .item rather than ['item']
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"""
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return self[item]
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@staticmethod
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@debug
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def cast(constant):
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"""
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cast string to int, float, eval or keep as string
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"""
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if hasattr(constant, 'startswith') and constant.startswith('0') \
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and '.' not in constant:
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return constant
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try:
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return int(constant)
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except ValueError:
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pass
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try:
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return float(constant)
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except ValueError:
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pass
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try:
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return eval(constant)
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except (NameError, SyntaxError):
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pass
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return constant
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@debug
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def __setitem__(self, item, value):
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"""
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dict like assignment - warns when a constant is changed
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"""
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if item in self.dict:
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warnings.warn('{0} changed to {1}'.format(item, value))
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self.dict[item] = value
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@debug
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def __setattr__(self, name, value):
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"""
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attribute assignment - warns when a constant is changed
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"""
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if hasattr(self, 'dict') and name in self.dict:
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warnings.warn('{0} changed to {1}'.format(name, value))
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self.dict[name] = value
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else:
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object.__setattr__(self, name, value)
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