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from __future__ import with_statement
'''
Created on Feb 27, 2012
@author: steger
'''
from DataProcessing.DataError import PrefixError
class PrefixManager(object):
'''
@summary: the unit prefix container
'''
class Prefix(object):
def __init__(self, reference, symbol, base, exponent):
'''
@summary: constructor
@param reference: the reference to the unit prefix
@type reference: str
@param symbol: a short form of the unit prefix
@type symbol: str
@param base: the base of the unit prefix, typically 2 or 10
@type base: int
@param exponent: the exponent of the unit prefix
@type exponent: int
'''
scale = base ** exponent
self._data = (reference, symbol, base, exponent, scale)
def __str__(self):
return self.symbol
def _get_reference(self):
return self._data[0]
def _get_symbol(self):
return self._data[1]
def _get_base(self):
return self._data[2]
def _get_exponent(self):
return self._data[3]
def _get_scale(self):
return self._data[4]
symbol = property(_get_symbol,None,None)
base = property(_get_base,None,None)
exponent = property(_get_exponent,None,None)
reference = property(_get_reference,None,None)
scale = property(_get_scale,None,None)
def __init__(self):
'''
@summary: constructor
'''
self.prefixes = {}
self.duplicatesymbols = set()
def __contains__(self, item):
'''
@summary: check the existence of a unit prefix
@param item: a unit prefix or its symbol
@type item: Prefix or str
@return: True if the prefix is known by the PrefixManager
@rtype: bool
@raise PrefixError: Wrong item type
'''
if isinstance(item, self.Prefix):
return item in self.prefixes.values()
elif isinstance(item, str):
for prefix in self.prefixes.values():
if prefix.symbol == item:
return True
return False
else:
raise PrefixError("Wrong item type %s" % item)
def __len__(self):
'''
@summary: the number of prefixes known by the PrefixManager
@return: the number of prefixes known by the PrefixManager
@rtype: int
'''
return len(self.prefixes)
def newPrefix(self, reference, symbol, base, exponent):
'''
@summary: generate a new unit prefix
@param reference: the reference to the unit prefix
@type reference: str
@param symbol: a short form of the unit prefix
@type symbol: str
@param base: the base of the unit prefix, typically 2 or 10
@type base: int
@param exponent: the exponent of the unit prefix
@type exponent: int
@return: the new unit prefix
@rtype: Prefix
@raise PrefixError: Prefix with reference exists
'''
if self.prefixes.has_key(reference):
raise PrefixError("Prefix with reference %s already exists" % reference)
if PrefixManager.__contains__(self, symbol):
self.duplicatesymbols.add(symbol)
prefix = self.Prefix(reference, symbol, base, exponent)
self.prefixes[reference] = prefix
return prefix
def __getitem__(self, reference):
'''
@summary: look up the prefix in the PrefixManager based on its reference
@param reference: the reference to the unit prefix
@type reference: str
@return: the unit prefix found
@rtype: Prefix
@raise PrefixError: Prefix with reference not found
'''
if self.prefixes.has_key(reference):
return self.prefixes[reference]
raise PrefixError("Prefix with reference %s not found" % reference)
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