"""
Spreadsheet example adapted from Raymond Hettinger's `recipe`__

__ http://code.activestate.com/recipes/355045-spreadsheet/

Demonstration::

    >>> from math import sin, pi
    >>> ss = Spreadsheet(sin=sin, pi=pi, abs=abs)
    >>> ss['a1'] = '-5'
    >>> ss['a2'] = 'a1*6'
    >>> ss['a3'] = 'a2*7'
    >>> ss['a3']
    -210
    >>> ss['b1'] = 'sin(pi/4)'
    >>> ss['b1']  # doctest:+ELLIPSIS
    0.707106781186...
    >>> ss.getformula('b1')
    'sin(pi/4)'
    >>> ss['c1'] = 'abs(a2)'
    >>> ss['c1']
    30
    >>> ss['c2'] = 'len(a2)'
    >>> ss['c2']
    Traceback (most recent call last):
      ...
    NameError: name 'len' is not defined
    >>> ss['d1'] = '3*'
    Traceback (most recent call last):
      ...
    SyntaxError: unexpected EOF while parsing ['d1'] = '3*'
"""


class Spreadsheet:

    def __init__(self, **tools):
        self._cells = {}
        self._tools = {'__builtins__' : {}}
        self._tools.update(tools)

    def __setitem__(self, key, formula):
        try:
            compile(formula, '<__setitem__>', 'eval')
        except SyntaxError as exc:
            msg = '{} [{!r}] = {!r}'.format(exc.msg, key, formula)
            raise SyntaxError(msg)
        self._cells[key] = formula

    def getformula(self, key):
        return self._cells[key]

    def __getitem__(self, key):
        return eval(self._cells[key], self._tools, self)