Replace long if-else blocks with look-up tables.

I see some long if-else blocks in the code. It would make sense to replace these with dictionary look-ups.

# OLD/CURRENT CODE:

def update_fpointer(self, nid, mode=ADD, replace=None):
   if mode is self.ADD:
        pass
    elif mode is self.DELETE:
        pass
    elif mode is self.INSERT: 
        pass
    elif mode is self.REPLACE:
        pass

# IDEA FOR NEW CODE
class node:
    #: Mode constants for routine `update_fpointer()`.
    (ADD, DELETE, INSERT, REPLACE) = list(range(4))
    fpointer_lookup_table = {ADD: "append", DELETE: "remove", INSERT: "append", REPLACE: "replace"}

    def update_fpointer(self, nid, mode=ADD, replace=None):
        f_name = self.fpointer_lookup_table[mode]
        f = gettattr(self, f_name)
        args = update_fpointer_arg_select(nid, mode, replace)
        return f(*args)

    def replace(self, nid, replacement)
    if replace is None:
        raise NodePropertyError(
            'Argument "replace" should be provided when mode is {}'.format(mode)
        )
    ind = self._fpointer.index(nid)
    self._fpointer[ind] = replace

A second example:

# OLD CODE
    @fpointer.setter
    def fpointer(self, value):
        """Set the value of `_fpointer`."""
        if value is None:
            self._fpointer = list()
        elif isinstance(value, list):
            self._fpointer = value
        elif isinstance(value, dict):
            self._fpointer = list(value.keys())
        elif isinstance(value, set):
            self._fpointer = list(value)
        else:  # TODO: add deprecated routine
            pass

# IDEA FOR NEW CODE
class node:

    # fpointer_setter_lookup_table = {"NoneType":lambda x: list(), "list":lambda x : x, etc....}

    @fpointer.setter
    def fpointer(self, value):
        """Set the value of `_fpointer`."""
        imp = fpointer_setter_lookup_table[value.__class__.__name__]
        self._fpointer = imp(value)

caesar0301 / treelib

Replace long if-else blocks with look-up tables. #109