>>> from frozenlist import FrozenList
>>> fl = FrozenList([17, 42])
>>> fl.append('spam')
>>> fl.append('Vikings')
>>> fl
<FrozenList(frozen=False, [17, 42, 'spam', 'Vikings'])>
>>> fl.freeze()
>>> fl
<FrozenList(frozen=True, [17, 42, 'spam', 'Vikings'])>
>>> fl.frozen
True
>>> fl.append("Monty")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "frozenlist/_frozenlist.pyx", line 97, in frozenlist._frozenlist.FrozenList.append
    self._check_frozen()
  File "frozenlist/_frozenlist.pyx", line 19, in frozenlist._frozenlist.FrozenList._check_frozen
    raise RuntimeError("Cannot modify frozen list.")
RuntimeError: Cannot modify frozen list.

>>> fl = FrozenList([17, 42, 'spam'])
>>> hash(fl)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "frozenlist/_frozenlist.pyx", line 111, in frozenlist._frozenlist.FrozenList.__hash__
    raise RuntimeError("Cannot hash unfrozen list.")
RuntimeError: Cannot hash unfrozen list.
>>> fl.freeze()
>>> hash(fl)
3713081631934410656
>>> dictionary = {fl: 'Vikings'} # frozen fl can be a dict key
>>> dictionary
{<FrozenList(frozen=True, [1, 2])>: 'Vikings'}