Class _WisdomBankSingleton

numexpr3/ne3compiler.py:1435–1504

The wisdomBank connects strings to their NumExpr objects, so if the same expression pattern is called, it will be retrieved from the bank. Also this permits serialization via pickle.

class _WisdomBankSingleton(dict):
    '''
    The wisdomBank connects strings to their NumExpr objects, so if the same 
    expression pattern is called, it will be retrieved from the bank.
    Also this permits serialization via pickle.
    '''

    def __init__(self, wisdomFile: str='', maxEntries: int=256):
        # Call super
        super(_WisdomBankSingleton, self).__init__(self)
        # attribute dictionary breaks a lot of things in the intepreter
        # dict.__init__(self)
        self.__wisdomFile = wisdomFile
        self.maxEntries = maxEntries
        pass
    
    @property 
    def wisdomFile(self) -> str:
        if not bool(self.__wisdomFile):
            if not os.access('ne3_wisdom.pkl', os.W_OK):
                raise OSError('insufficient permissions to write to {}'.format('ne3_wisdom.pkl'))
            self.__wisdomFile = 'ne3_wisdom.pkl'
        return self.__wisdomFile
    
    @wisdomFile.setter
    def wisdomFile(self, newName: str) -> None:
        '''Check to see if the user has write permisions on the file.'''
        dirName = os.path.dirname(newName)
        if not os.access(dirName, os.W_OK):
            raise OSError('do not have write perimission for directory {}'.format(dirName))
        self.__wisdomFile = newName
    
    def __setitem__(self, key, value):
        # Protection against growing the cache too much
        if len(self) > self.maxEntries:
            # Remove a 10% of random elements from the cache
            entries_to_remove = self.maxEntries // 10

            keysView = list(self.keys())
            for I, cull in enumerate(keysView):
                self.pop(cull)
                if I >= entries_to_remove: 
                    break
                
        super(_WisdomBankSingleton, self).__setitem__(key, value)
         

    def load(self, wisdomFile: Optional[str]=None) -> None:
        '''
        Load the wisdom from a file on disk (or otherwise file-like object).

        wisdomFile should support the :code:`io.IOBase` or similar interface.
        '''
        if wisdomFile == None:
            wisdomFile = self.wisdomFile
            
        with open(wisdomFile, 'rb') as fh:
            self = pickle.load(fh)