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views.py
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views.py
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# -*- coding: utf-8 -*-
"""
Copyright (C) Koos Zevenhoven.
See LICENSE.txt at http://github.com/k7hoven/views for license information.
@author: Koos Zevenhoven
"""
__all__ = ['gen', 'seq']
def make(callable):
return callable()
@make
class gen:
"""Generator comprehension syntax.
Example:
>>> list(gen[::range(3), 3, 4, ::range(5,7), 7])
[0, 1, 2, 3, 4, 5, 6, 7]
"""
def __getitem__(self, args):
if not isinstance(args, tuple):
args = args,
@tuple
@make
def parts():
part = []
for obj in args:
if isinstance(obj, slice):
if obj.start is None and obj.stop is None:
obj = obj.step
objtype = type(obj)
if hasattr(objtype, '__iter__'):
obj = iter(obj)
if not hasattr(type(obj), '__next__'):
raise TypeError(
f"'{objtype.__name__}' object is not "
"iterable and cannot be chained"
)
if part:
yield part
part = []
yield obj
else:
raise SyntaxError(
'invalid syntax in generator comprehension'
)
else:
part.append(obj)
if part:
yield part
return self.chain(*parts)
@staticmethod
def chain(*parts):
for part in parts:
yield from part
chain.__qualname__ = '<views.gen>'
class LengthChangedError(RuntimeError):
pass
def issequence(obj):
otype = type(obj)
return hasattr(otype, '__getitem__') and hasattr(otype, '__len__')
class Repr(str):
def __repr__(self):
return self
class SeqMixin:
REPR_ITEMS = 10
REPR_SPLIT = 5, 4
def __repr__(self):
template = f"<sequence view {len(self)}:" " {} >"
if len(self) <= self.REPR_ITEMS:
return template.format(repr([*self]))
return template.format(
repr([*self[:self.REPR_SPLIT[0]],
Repr("..."),
*self[-self.REPR_SPLIT[1]:]])
)
class Seq(SeqMixin):
def __init__(self, seq, start=None, stop=None, step=None):
if not issequence(seq):
raise TypeError(
f"'{type(seq).__name__}' object is not a sequence"
)
self._seq = seq
self._len_orig = len(seq)
self._slice = slice(*slice(start, stop, step).indices(len(seq)))
self._len = len(range(self._len_orig)[self._slice])
@property
def deps(self):
return self._seq,
def __len__(self):
return self._len
def __getitem__(self, subscript):
if isinstance(subscript, tuple):
raise TypeError("multi-indices not supperted")
if len(self._seq) != self._len_orig:
raise LengthChangedError(
"length of underlying sequence has changed"
)
if isinstance(subscript, slice):
idx = subscript.indices(len(self))
start = self._slice.start + idx[0] * self._slice.step
stop = start + self._slice.step * (idx[1] - idx[0])
step = self._slice.step * idx[2]
return SeqView(self._seq, start, stop, step)
try:
subscript.__index__
except AttributeError:
raise TypeError(
"index must be an integer, a slice or have an __index__ method"
) from None
subscript = subscript.__index__()
if subscript < 0:
subscript = self._len + subscript
if subscript < 0 or subscript >= self._len:
raise IndexError("index out of range")
return self._seq[self._slice.start + subscript * self._slice.step]
class SeqChain(SeqMixin):
def __init__(self, *parts):
_len = 0
for p in parts:
if not issequence(p):
raise TypeError(
f"'{type(p).__name__}' object is not a sequence"
)
_len += len(p)
self._parts = parts
self._len = _len
@property
def deps(self):
return self._parts
def __len__(self):
return self._len
def _find_position(self, index):
start = 0
if index < 0 or index >= self._len:
return None
for i, p in enumerate(self._parts):
newstart = start + len(p)
if start <= index < newstart:
ret = (i, index - start)
start = newstart
if not start == self._len:
raise LengthChangedError(
"length of one of chained sequences has changed"
)
return ret
def __getitem__(self, subscript):
if isinstance(subscript, tuple):
raise TypeError("multi-indices not supperted")
if isinstance(subscript, slice):
# Memory use could be optimized further by making a smarter
# slice which does not hold references to unused parts
return Seq(self, subscript.start, subscript.stop, subscript.step)
try:
subscript.__index__
except AttributeError:
raise TypeError(
"index must be an integer, a slice or have an __index__ method"
) from None
pos = self._find_position(subscript.__index__())
if pos is None:
raise IndexError("sequence index out of bounds")
return self._parts[pos[0]][pos[1]]
@make
class seq:
"""Sequence view comprehension syntax.
Resulting objects support slicing and indexing.
Examples:
>>> seq[::range(3), None, ::"abc", "Hi!"]
<sequence view 8: [0, 1, 2, None, 'a', 'b', 'c', 'Hi!'] >
>>> seq[::range(100)]
<sequence view 100: [0, 1, 2, 3, 4, ..., 96, 97, 98, 99] >
"""
def __getitem__(self, args):
if not isinstance(args, tuple):
args = args,
@tuple
@make
def parts():
part = []
for obj in args:
if isinstance(obj, slice):
if obj.start is None and obj.stop is None:
obj = obj.step
if not issequence(obj):
raise TypeError(
f"'{type(obj).__name__}' object is not "
"a sequence and cannot be chained"
)
if part:
yield part
part = []
yield obj
else:
raise SyntaxError(
'Invalid syntax in chain generator expression'
)
else:
part.append(obj)
if part:
yield part
return SeqChain(*parts)
chain = staticmethod(SeqChain)
_range = range
class range:
def __new__(cls, *args, **kwargs):
if ... not in args:
return cls._from_std_range(_range(*args, **kwargs))
start = args[0]
ind = args.index(...)
if ind == 1:
if len(args) != 3:
if len(args) > 3:
raise TypeError(
"too many arguments to "
"range(first, ..., last [, step=step])"
)
elif len(args) < 3:
raise TypeError(
"missing last value for "
"range(first, ..., last[, step=step])"
)
step = kwargs.pop('step', 1)
last = args[2]
elif ind == 2:
if len(args) != 4:
if len(args) > 4:
raise TypeError(
"too many arguments to "
"range(first, second, ..., last)"
)
elif len(args) < 4:
raise TypeError(
"missing last value for "
"range(first, second, ..., last)"
)
step = args[1] - start
last = args[3]
if 'step' in kwargs:
if kwargs['step'] == step:
raise TypeError("redundant 'step' argument")
else:
raise TypeError("conflicting 'step' argument")
elif ind == 0:
raise TypeError("missing first value for range(first, ..., last)")
elif ind > 2:
raise TypeError("misplaced ellipsis (...)")
else:
assert False # Should never get here
if step > 0:
stop = last + 1
if stop < start:
raise ValueError(
"expected negative step for {}, ..., {}"
.format(start, last)
)
else:
stop = last - 1
if stop > start:
raise ValueError(
"expected positive step for {}, ..., {}"
.format(start, last)
)
if kwargs:
raise TypeError(
"unexpected keyword argument(s): {}"\
.format(", ".join(kwargs.keys()))
)
return cls._from_std_range(_range(start, stop, step))
@classmethod
def _from_std_range(cls, rng):
new = object.__new__(cls)
new._range = rng
return new
def __repr__(self):
template = "range({}, ..., {}{})"
if self._range.step == 1:
stepstr = ""
else:
stepstr = ", step={}".format(self._range.step)
try:
return template.format(self[0], self[-1], stepstr)
except IndexError:
return repr(self._range)
@property
def start(self):
return self._range.start
@property
def stop(self):
return self._range.stop
@property
def step(self):
return self._range.step
from types import MethodType as _MethodType
import functools as _functools
def _inject_range_methods():
_dont_copy = ['__getattribute__', '__init__'] + list(vars(range))
def make_range_method(function):
@_functools.wraps(function)
def method(self, *args, **kwargs):
ret = function(self._range, *args, **kwargs)
if type(ret) is _range:
return range._from_std_range(ret)
return ret
return method
for name, function in vars(_range).items():
if hasattr(function, '__call__') and name not in _dont_copy:
setattr(range, name, make_range_method(function))
_inject_range_methods()