"""
A list subclass for Python 2 that behaves like Python 3's list.
The primary difference is that lists have a .copy() method in Py3.
Example use:
>>> from builtins import list
>>> l1 = list() # instead of {} for an empty list
>>> l1.append('hello')
>>> l2 = l1.copy()
"""
import sys
import copy
from future.utils import with_metaclass
from future.types.newobject import newobject
_builtin_list = list
ver = sys.version_info[:2]
class BaseNewList(type):
def __instancecheck__(cls, instance):
if cls == newlist:
return isinstance(instance, _builtin_list)
else:
return issubclass(instance.__class__, cls)
class newlist(with_metaclass(BaseNewList, _builtin_list)):
"""
A backport of the Python 3 list object to Py2
"""
def copy(self):
"""
L.copy() -> list -- a shallow copy of L
"""
return copy.copy(self)
def clear(self):
"""L.clear() -> None -- remove all items from L"""
for i in range(len(self)):
self.pop()
def __new__(cls, *args, **kwargs):
"""
list() -> new empty list
list(iterable) -> new list initialized from iterable's items
"""
if len(args) == 0:
return super(newlist, cls).__new__(cls)
elif type(args[0]) == newlist:
value = args[0]
else:
value = args[0]
return super(newlist, cls).__new__(cls, value)
def __add__(self, value):
return newlist(super(newlist, self).__add__(value))
def __radd__(self, left):
" left + self "
try:
return newlist(left) + self
except:
return NotImplemented
def __getitem__(self, y):
"""
x.__getitem__(y) <==> x[y]
Warning: a bug in Python 2.x prevents indexing via a slice from
returning a newlist object.
"""
if isinstance(y, slice):
return newlist(super(newlist, self).__getitem__(y))
else:
return super(newlist, self).__getitem__(y)
def __native__(self):
"""
Hook for the future.utils.native() function
"""
return list(self)
def __nonzero__(self):
return len(self) > 0
__all__ = ['newlist']