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558 lines
16 KiB
558 lines
16 KiB
"""
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Cycler
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======
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Cycling through combinations of values, producing dictionaries.
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You can add cyclers::
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from cycler import cycler
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cc = (cycler(color=list('rgb')) +
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cycler(linestyle=['-', '--', '-.']))
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for d in cc:
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print(d)
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Results in::
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{'color': 'r', 'linestyle': '-'}
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{'color': 'g', 'linestyle': '--'}
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{'color': 'b', 'linestyle': '-.'}
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You can multiply cyclers::
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from cycler import cycler
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cc = (cycler(color=list('rgb')) *
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cycler(linestyle=['-', '--', '-.']))
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for d in cc:
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print(d)
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Results in::
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{'color': 'r', 'linestyle': '-'}
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{'color': 'r', 'linestyle': '--'}
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{'color': 'r', 'linestyle': '-.'}
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{'color': 'g', 'linestyle': '-'}
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{'color': 'g', 'linestyle': '--'}
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{'color': 'g', 'linestyle': '-.'}
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{'color': 'b', 'linestyle': '-'}
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{'color': 'b', 'linestyle': '--'}
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{'color': 'b', 'linestyle': '-.'}
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"""
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from __future__ import (absolute_import, division, print_function,
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unicode_literals)
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import six
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from itertools import product, cycle
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from six.moves import zip, reduce
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from operator import mul, add
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import copy
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__version__ = '0.10.0'
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def _process_keys(left, right):
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"""
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Helper function to compose cycler keys
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Parameters
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----------
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left, right : iterable of dictionaries or None
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The cyclers to be composed
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Returns
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-------
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keys : set
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The keys in the composition of the two cyclers
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"""
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l_peek = next(iter(left)) if left is not None else {}
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r_peek = next(iter(right)) if right is not None else {}
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l_key = set(l_peek.keys())
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r_key = set(r_peek.keys())
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if l_key & r_key:
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raise ValueError("Can not compose overlapping cycles")
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return l_key | r_key
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class Cycler(object):
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"""
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Composable cycles
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This class has compositions methods:
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``+``
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for 'inner' products (zip)
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``+=``
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in-place ``+``
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``*``
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for outer products (itertools.product) and integer multiplication
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``*=``
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in-place ``*``
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and supports basic slicing via ``[]``
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Parameters
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----------
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left : Cycler or None
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The 'left' cycler
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right : Cycler or None
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The 'right' cycler
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op : func or None
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Function which composes the 'left' and 'right' cyclers.
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"""
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def __call__(self):
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return cycle(self)
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def __init__(self, left, right=None, op=None):
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"""Semi-private init
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Do not use this directly, use `cycler` function instead.
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"""
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if isinstance(left, Cycler):
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self._left = Cycler(left._left, left._right, left._op)
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elif left is not None:
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# Need to copy the dictionary or else that will be a residual
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# mutable that could lead to strange errors
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self._left = [copy.copy(v) for v in left]
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else:
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self._left = None
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if isinstance(right, Cycler):
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self._right = Cycler(right._left, right._right, right._op)
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elif right is not None:
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# Need to copy the dictionary or else that will be a residual
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# mutable that could lead to strange errors
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self._right = [copy.copy(v) for v in right]
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else:
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self._right = None
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self._keys = _process_keys(self._left, self._right)
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self._op = op
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@property
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def keys(self):
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"""
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The keys this Cycler knows about
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"""
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return set(self._keys)
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def change_key(self, old, new):
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"""
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Change a key in this cycler to a new name.
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Modification is performed in-place.
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Does nothing if the old key is the same as the new key.
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Raises a ValueError if the new key is already a key.
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Raises a KeyError if the old key isn't a key.
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"""
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if old == new:
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return
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if new in self._keys:
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raise ValueError("Can't replace %s with %s, %s is already a key" %
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(old, new, new))
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if old not in self._keys:
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raise KeyError("Can't replace %s with %s, %s is not a key" %
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(old, new, old))
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self._keys.remove(old)
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self._keys.add(new)
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if self._right is not None and old in self._right.keys:
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self._right.change_key(old, new)
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# self._left should always be non-None
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# if self._keys is non-empty.
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elif isinstance(self._left, Cycler):
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self._left.change_key(old, new)
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else:
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# It should be completely safe at this point to
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# assume that the old key can be found in each
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# iteration.
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self._left = [{new: entry[old]} for entry in self._left]
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def _compose(self):
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"""
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Compose the 'left' and 'right' components of this cycle
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with the proper operation (zip or product as of now)
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"""
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for a, b in self._op(self._left, self._right):
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out = dict()
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out.update(a)
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out.update(b)
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yield out
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@classmethod
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def _from_iter(cls, label, itr):
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"""
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Class method to create 'base' Cycler objects
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that do not have a 'right' or 'op' and for which
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the 'left' object is not another Cycler.
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Parameters
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----------
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label : str
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The property key.
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itr : iterable
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Finite length iterable of the property values.
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Returns
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-------
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cycler : Cycler
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New 'base' `Cycler`
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"""
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ret = cls(None)
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ret._left = list({label: v} for v in itr)
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ret._keys = set([label])
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return ret
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def __getitem__(self, key):
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# TODO : maybe add numpy style fancy slicing
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if isinstance(key, slice):
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trans = self.by_key()
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return reduce(add, (_cycler(k, v[key])
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for k, v in six.iteritems(trans)))
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else:
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raise ValueError("Can only use slices with Cycler.__getitem__")
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def __iter__(self):
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if self._right is None:
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return iter(dict(l) for l in self._left)
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return self._compose()
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def __add__(self, other):
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"""
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Pair-wise combine two equal length cycles (zip)
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Parameters
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----------
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other : Cycler
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The second Cycler
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"""
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if len(self) != len(other):
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raise ValueError("Can only add equal length cycles, "
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"not {0} and {1}".format(len(self), len(other)))
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return Cycler(self, other, zip)
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def __mul__(self, other):
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"""
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Outer product of two cycles (`itertools.product`) or integer
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multiplication.
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Parameters
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----------
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other : Cycler or int
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The second Cycler or integer
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"""
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if isinstance(other, Cycler):
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return Cycler(self, other, product)
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elif isinstance(other, int):
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trans = self.by_key()
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return reduce(add, (_cycler(k, v*other)
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for k, v in six.iteritems(trans)))
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else:
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return NotImplemented
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def __rmul__(self, other):
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return self * other
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def __len__(self):
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op_dict = {zip: min, product: mul}
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if self._right is None:
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return len(self._left)
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l_len = len(self._left)
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r_len = len(self._right)
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return op_dict[self._op](l_len, r_len)
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def __iadd__(self, other):
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"""
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In-place pair-wise combine two equal length cycles (zip)
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Parameters
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----------
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other : Cycler
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The second Cycler
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"""
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if not isinstance(other, Cycler):
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raise TypeError("Cannot += with a non-Cycler object")
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# True shallow copy of self is fine since this is in-place
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old_self = copy.copy(self)
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self._keys = _process_keys(old_self, other)
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self._left = old_self
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self._op = zip
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self._right = Cycler(other._left, other._right, other._op)
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return self
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def __imul__(self, other):
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"""
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In-place outer product of two cycles (`itertools.product`)
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Parameters
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----------
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other : Cycler
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The second Cycler
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"""
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if not isinstance(other, Cycler):
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raise TypeError("Cannot *= with a non-Cycler object")
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# True shallow copy of self is fine since this is in-place
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old_self = copy.copy(self)
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self._keys = _process_keys(old_self, other)
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self._left = old_self
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self._op = product
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self._right = Cycler(other._left, other._right, other._op)
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return self
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def __eq__(self, other):
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"""
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Check equality
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"""
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if len(self) != len(other):
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return False
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if self.keys ^ other.keys:
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return False
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return all(a == b for a, b in zip(self, other))
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def __repr__(self):
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op_map = {zip: '+', product: '*'}
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if self._right is None:
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lab = self.keys.pop()
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itr = list(v[lab] for v in self)
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return "cycler({lab!r}, {itr!r})".format(lab=lab, itr=itr)
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else:
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op = op_map.get(self._op, '?')
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msg = "({left!r} {op} {right!r})"
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return msg.format(left=self._left, op=op, right=self._right)
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def _repr_html_(self):
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# an table showing the value of each key through a full cycle
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output = "<table>"
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sorted_keys = sorted(self.keys, key=repr)
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for key in sorted_keys:
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output += "<th>{key!r}</th>".format(key=key)
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for d in iter(self):
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output += "<tr>"
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for k in sorted_keys:
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output += "<td>{val!r}</td>".format(val=d[k])
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output += "</tr>"
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output += "</table>"
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return output
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def by_key(self):
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"""Values by key
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This returns the transposed values of the cycler. Iterating
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over a `Cycler` yields dicts with a single value for each key,
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this method returns a `dict` of `list` which are the values
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for the given key.
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The returned value can be used to create an equivalent `Cycler`
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using only `+`.
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Returns
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-------
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transpose : dict
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dict of lists of the values for each key.
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"""
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# TODO : sort out if this is a bottle neck, if there is a better way
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# and if we care.
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keys = self.keys
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# change this to dict comprehension when drop 2.6
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out = dict((k, list()) for k in keys)
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for d in self:
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for k in keys:
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out[k].append(d[k])
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return out
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# for back compatibility
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_transpose = by_key
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def simplify(self):
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"""Simplify the Cycler
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Returned as a composition using only sums (no multiplications)
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Returns
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-------
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simple : Cycler
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An equivalent cycler using only summation"""
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# TODO: sort out if it is worth the effort to make sure this is
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# balanced. Currently it is is
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# (((a + b) + c) + d) vs
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# ((a + b) + (c + d))
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# I would believe that there is some performance implications
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trans = self.by_key()
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return reduce(add, (_cycler(k, v) for k, v in six.iteritems(trans)))
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def concat(self, other):
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"""Concatenate this cycler and an other.
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The keys must match exactly.
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This returns a single Cycler which is equivalent to
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`itertools.chain(self, other)`
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Examples
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--------
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>>> num = cycler('a', range(3))
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>>> let = cycler('a', 'abc')
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>>> num.concat(let)
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cycler('a', [0, 1, 2, 'a', 'b', 'c'])
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Parameters
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----------
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other : `Cycler`
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The `Cycler` to concatenate to this one.
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Returns
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-------
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ret : `Cycler`
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The concatenated `Cycler`
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"""
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return concat(self, other)
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def concat(left, right):
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"""Concatenate two cyclers.
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The keys must match exactly.
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This returns a single Cycler which is equivalent to
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`itertools.chain(left, right)`
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Examples
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--------
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>>> num = cycler('a', range(3))
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>>> let = cycler('a', 'abc')
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>>> num.concat(let)
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cycler('a', [0, 1, 2, 'a', 'b', 'c'])
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Parameters
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----------
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left, right : `Cycler`
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The two `Cycler` instances to concatenate
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Returns
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-------
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ret : `Cycler`
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The concatenated `Cycler`
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"""
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if left.keys != right.keys:
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msg = '\n\t'.join(["Keys do not match:",
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"Intersection: {both!r}",
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"Disjoint: {just_one!r}"]).format(
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both=left.keys & right.keys,
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just_one=left.keys ^ right.keys)
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raise ValueError(msg)
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_l = left.by_key()
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_r = right.by_key()
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return reduce(add, (_cycler(k, _l[k] + _r[k]) for k in left.keys))
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def cycler(*args, **kwargs):
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"""
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Create a new `Cycler` object from a single positional argument,
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a pair of positional arguments, or the combination of keyword arguments.
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cycler(arg)
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cycler(label1=itr1[, label2=iter2[, ...]])
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cycler(label, itr)
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Form 1 simply copies a given `Cycler` object.
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Form 2 composes a `Cycler` as an inner product of the
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pairs of keyword arguments. In other words, all of the
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iterables are cycled simultaneously, as if through zip().
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Form 3 creates a `Cycler` from a label and an iterable.
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This is useful for when the label cannot be a keyword argument
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(e.g., an integer or a name that has a space in it).
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Parameters
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----------
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arg : Cycler
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Copy constructor for Cycler (does a shallow copy of iterables).
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label : name
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The property key. In the 2-arg form of the function,
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the label can be any hashable object. In the keyword argument
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form of the function, it must be a valid python identifier.
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itr : iterable
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Finite length iterable of the property values.
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Can be a single-property `Cycler` that would
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be like a key change, but as a shallow copy.
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Returns
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-------
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cycler : Cycler
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New `Cycler` for the given property
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"""
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if args and kwargs:
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raise TypeError("cyl() can only accept positional OR keyword "
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"arguments -- not both.")
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if len(args) == 1:
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if not isinstance(args[0], Cycler):
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raise TypeError("If only one positional argument given, it must "
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" be a Cycler instance.")
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return Cycler(args[0])
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elif len(args) == 2:
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return _cycler(*args)
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elif len(args) > 2:
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raise TypeError("Only a single Cycler can be accepted as the lone "
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"positional argument. Use keyword arguments instead.")
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if kwargs:
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return reduce(add, (_cycler(k, v) for k, v in six.iteritems(kwargs)))
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raise TypeError("Must have at least a positional OR keyword arguments")
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def _cycler(label, itr):
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"""
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Create a new `Cycler` object from a property name and
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iterable of values.
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Parameters
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----------
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label : hashable
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The property key.
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itr : iterable
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Finite length iterable of the property values.
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Returns
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-------
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cycler : Cycler
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New `Cycler` for the given property
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"""
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if isinstance(itr, Cycler):
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keys = itr.keys
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if len(keys) != 1:
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msg = "Can not create Cycler from a multi-property Cycler"
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raise ValueError(msg)
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lab = keys.pop()
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# Doesn't need to be a new list because
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# _from_iter() will be creating that new list anyway.
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itr = (v[lab] for v in itr)
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return Cycler._from_iter(label, itr)
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