"""
Cycler
======
Cycling through combinations of values, producing dictionaries.
You can add cyclers::
from cycler import cycler
cc = (cycler(color=list('rgb')) +
cycler(linestyle=['-', '--', '-.']))
for d in cc:
print(d)
Results in::
{'color': 'r', 'linestyle': '-'}
{'color': 'g', 'linestyle': '--'}
{'color': 'b', 'linestyle': '-.'}
You can multiply cyclers::
from cycler import cycler
cc = (cycler(color=list('rgb')) *
cycler(linestyle=['-', '--', '-.']))
for d in cc:
print(d)
Results in::
{'color': 'r', 'linestyle': '-'}
{'color': 'r', 'linestyle': '--'}
{'color': 'r', 'linestyle': '-.'}
{'color': 'g', 'linestyle': '-'}
{'color': 'g', 'linestyle': '--'}
{'color': 'g', 'linestyle': '-.'}
{'color': 'b', 'linestyle': '-'}
{'color': 'b', 'linestyle': '--'}
{'color': 'b', 'linestyle': '-.'}
"""
from __future__ import annotations
from collections.abc import Hashable, Iterable, Generator
import copy
from functools import reduce
from itertools import product, cycle
from operator import mul, add
# Dict, List, Union required for runtime cast calls
from typing import TypeVar, Generic, Callable, Union, Dict, List, Any, overload, cast
__version__ = "0.12.1"
K = TypeVar("K", bound=Hashable)
L = TypeVar("L", bound=Hashable)
V = TypeVar("V")
U = TypeVar("U")
def _process_keys(
left: Cycler[K, V] | Iterable[dict[K, V]],
right: Cycler[K, V] | Iterable[dict[K, V]] | None,
) -> set[K]:
"""
Helper function to compose cycler keys.
Parameters
----------
left, right : iterable of dictionaries or None
The cyclers to be composed.
Returns
-------
keys : set
The keys in the composition of the two cyclers.
"""
l_peek: dict[K, V] = next(iter(left)) if left != [] else {}
r_peek: dict[K, V] = next(iter(right)) if right is not None else {}
l_key: set[K] = set(l_peek.keys())
r_key: set[K] = set(r_peek.keys())
if l_key & r_key:
raise ValueError("Can not compose overlapping cycles")
return l_key | r_key
[docs]
def concat(left: Cycler[K, V], right: Cycler[K, U]) -> Cycler[K, V | U]:
r"""
Concatenate `Cycler`\s, as if chained using `itertools.chain`.
The keys must match exactly.
Examples
--------
>>> num = cycler('a', range(3))
>>> let = cycler('a', 'abc')
>>> num.concat(let)
cycler('a', [0, 1, 2, 'a', 'b', 'c'])
Returns
-------
`Cycler`
The concatenated cycler.
"""
if left.keys != right.keys:
raise ValueError(
"Keys do not match:\n"
"\tIntersection: {both!r}\n"
"\tDisjoint: {just_one!r}".format(
both=left.keys & right.keys, just_one=left.keys ^ right.keys
)
)
_l = cast(Dict[K, List[Union[V, U]]], left.by_key())
_r = cast(Dict[K, List[Union[V, U]]], right.by_key())
return reduce(add, (_cycler(k, _l[k] + _r[k]) for k in left.keys))
[docs]
class Cycler(Generic[K, V]):
"""
Composable cycles.
This class has compositions methods:
``+``
for 'inner' products (zip)
``+=``
in-place ``+``
``*``
for outer products (`itertools.product`) and integer multiplication
``*=``
in-place ``*``
and supports basic slicing via ``[]``.
Parameters
----------
left, right : Cycler or None
The 'left' and 'right' cyclers.
op : func or None
Function which composes the 'left' and 'right' cyclers.
"""
def __call__(self):
return cycle(self)
[docs]
def __init__(
self,
left: Cycler[K, V] | Iterable[dict[K, V]] | None,
right: Cycler[K, V] | None = None,
op: Any = None,
):
"""
Semi-private init.
Do not use this directly, use `cycler` function instead.
"""
if isinstance(left, Cycler):
self._left: Cycler[K, V] | list[dict[K, V]] = Cycler(
left._left, left._right, left._op
)
elif left is not None:
# Need to copy the dictionary or else that will be a residual
# mutable that could lead to strange errors
self._left = [copy.copy(v) for v in left]
else:
self._left = []
if isinstance(right, Cycler):
self._right: Cycler[K, V] | None = Cycler(
right._left, right._right, right._op
)
else:
self._right = None
self._keys: set[K] = _process_keys(self._left, self._right)
self._op: Any = op
def __contains__(self, k):
return k in self._keys
@property
def keys(self) -> set[K]:
"""The keys this Cycler knows about."""
return set(self._keys)
[docs]
def change_key(self, old: K, new: K) -> None:
"""
Change a key in this cycler to a new name.
Modification is performed in-place.
Does nothing if the old key is the same as the new key.
Raises a ValueError if the new key is already a key.
Raises a KeyError if the old key isn't a key.
"""
if old == new:
return
if new in self._keys:
raise ValueError(
f"Can't replace {old} with {new}, {new} is already a key"
)
if old not in self._keys:
raise KeyError(
f"Can't replace {old} with {new}, {old} is not a key"
)
self._keys.remove(old)
self._keys.add(new)
if self._right is not None and old in self._right.keys:
self._right.change_key(old, new)
# self._left should always be non-None
# if self._keys is non-empty.
elif isinstance(self._left, Cycler):
self._left.change_key(old, new)
else:
# It should be completely safe at this point to
# assume that the old key can be found in each
# iteration.
self._left = [{new: entry[old]} for entry in self._left]
@classmethod
def _from_iter(cls, label: K, itr: Iterable[V]) -> Cycler[K, V]:
"""
Class method to create 'base' Cycler objects
that do not have a 'right' or 'op' and for which
the 'left' object is not another Cycler.
Parameters
----------
label : hashable
The property key.
itr : iterable
Finite length iterable of the property values.
Returns
-------
`Cycler`
New 'base' cycler.
"""
ret: Cycler[K, V] = cls(None)
ret._left = list({label: v} for v in itr)
ret._keys = {label}
return ret
def __getitem__(self, key: slice) -> Cycler[K, V]:
# TODO : maybe add numpy style fancy slicing
if isinstance(key, slice):
trans = self.by_key()
return reduce(add, (_cycler(k, v[key]) for k, v in trans.items()))
else:
raise ValueError("Can only use slices with Cycler.__getitem__")
def __iter__(self) -> Generator[dict[K, V], None, None]:
if self._right is None:
for left in self._left:
yield dict(left)
else:
if self._op is None:
raise TypeError(
"Operation cannot be None when both left and right are defined"
)
for a, b in self._op(self._left, self._right):
out = {}
out.update(a)
out.update(b)
yield out
def __add__(self, other: Cycler[L, U]) -> Cycler[K | L, V | U]:
"""
Pair-wise combine two equal length cyclers (zip).
Parameters
----------
other : Cycler
"""
if len(self) != len(other):
raise ValueError(
f"Can only add equal length cycles, not {len(self)} and {len(other)}"
)
return Cycler(
cast(Cycler[Union[K, L], Union[V, U]], self),
cast(Cycler[Union[K, L], Union[V, U]], other),
zip
)
@overload
def __mul__(self, other: Cycler[L, U]) -> Cycler[K | L, V | U]:
...
@overload
def __mul__(self, other: int) -> Cycler[K, V]:
...
def __mul__(self, other):
"""
Outer product of two cyclers (`itertools.product`) or integer
multiplication.
Parameters
----------
other : Cycler or int
"""
if isinstance(other, Cycler):
return Cycler(
cast(Cycler[Union[K, L], Union[V, U]], self),
cast(Cycler[Union[K, L], Union[V, U]], other),
product
)
elif isinstance(other, int):
trans = self.by_key()
return reduce(
add, (_cycler(k, v * other) for k, v in trans.items())
)
else:
return NotImplemented
@overload
def __rmul__(self, other: Cycler[L, U]) -> Cycler[K | L, V | U]:
...
@overload
def __rmul__(self, other: int) -> Cycler[K, V]:
...
def __rmul__(self, other):
return self * other
def __len__(self) -> int:
op_dict: dict[Callable, Callable[[int, int], int]] = {zip: min, product: mul}
if self._right is None:
return len(self._left)
l_len = len(self._left)
r_len = len(self._right)
return op_dict[self._op](l_len, r_len)
# iadd and imul do not exapand the the type as the returns must be consistent with
# self, thus they flag as inconsistent with add/mul
def __iadd__(self, other: Cycler[K, V]) -> Cycler[K, V]: # type: ignore[misc]
"""
In-place pair-wise combine two equal length cyclers (zip).
Parameters
----------
other : Cycler
"""
if not isinstance(other, Cycler):
raise TypeError("Cannot += with a non-Cycler object")
# True shallow copy of self is fine since this is in-place
old_self = copy.copy(self)
self._keys = _process_keys(old_self, other)
self._left = old_self
self._op = zip
self._right = Cycler(other._left, other._right, other._op)
return self
def __imul__(self, other: Cycler[K, V] | int) -> Cycler[K, V]: # type: ignore[misc]
"""
In-place outer product of two cyclers (`itertools.product`).
Parameters
----------
other : Cycler
"""
if not isinstance(other, Cycler):
raise TypeError("Cannot *= with a non-Cycler object")
# True shallow copy of self is fine since this is in-place
old_self = copy.copy(self)
self._keys = _process_keys(old_self, other)
self._left = old_self
self._op = product
self._right = Cycler(other._left, other._right, other._op)
return self
def __eq__(self, other: object) -> bool:
if not isinstance(other, Cycler):
return False
if len(self) != len(other):
return False
if self.keys ^ other.keys:
return False
return all(a == b for a, b in zip(self, other))
__hash__ = None # type: ignore
def __repr__(self) -> str:
op_map = {zip: "+", product: "*"}
if self._right is None:
lab = self.keys.pop()
itr = list(v[lab] for v in self)
return f"cycler({lab!r}, {itr!r})"
else:
op = op_map.get(self._op, "?")
msg = "({left!r} {op} {right!r})"
return msg.format(left=self._left, op=op, right=self._right)
def _repr_html_(self) -> str:
# an table showing the value of each key through a full cycle
output = "<table>"
sorted_keys = sorted(self.keys, key=repr)
for key in sorted_keys:
output += f"<th>{key!r}</th>"
for d in iter(self):
output += "<tr>"
for k in sorted_keys:
output += f"<td>{d[k]!r}</td>"
output += "</tr>"
output += "</table>"
return output
[docs]
def by_key(self) -> dict[K, list[V]]:
"""
Values by key.
This returns the transposed values of the cycler. Iterating
over a `Cycler` yields dicts with a single value for each key,
this method returns a `dict` of `list` which are the values
for the given key.
The returned value can be used to create an equivalent `Cycler`
using only `+`.
Returns
-------
transpose : dict
dict of lists of the values for each key.
"""
# TODO : sort out if this is a bottle neck, if there is a better way
# and if we care.
keys = self.keys
out: dict[K, list[V]] = {k: list() for k in keys}
for d in self:
for k in keys:
out[k].append(d[k])
return out
# for back compatibility
_transpose = by_key
[docs]
def simplify(self) -> Cycler[K, V]:
"""
Simplify the cycler into a sum (but no products) of cyclers.
Returns
-------
simple : Cycler
"""
# TODO: sort out if it is worth the effort to make sure this is
# balanced. Currently it is is
# (((a + b) + c) + d) vs
# ((a + b) + (c + d))
# I would believe that there is some performance implications
trans = self.by_key()
return reduce(add, (_cycler(k, v) for k, v in trans.items()))
concat = concat
@overload
def cycler(arg: Cycler[K, V]) -> Cycler[K, V]:
...
@overload
def cycler(**kwargs: Iterable[V]) -> Cycler[str, V]:
...
@overload
def cycler(label: K, itr: Iterable[V]) -> Cycler[K, V]:
...
[docs]
def cycler(*args, **kwargs):
"""
Create a new `Cycler` object from a single positional argument,
a pair of positional arguments, or the combination of keyword arguments.
cycler(arg)
cycler(label1=itr1[, label2=iter2[, ...]])
cycler(label, itr)
Form 1 simply copies a given `Cycler` object.
Form 2 composes a `Cycler` as an inner product of the
pairs of keyword arguments. In other words, all of the
iterables are cycled simultaneously, as if through zip().
Form 3 creates a `Cycler` from a label and an iterable.
This is useful for when the label cannot be a keyword argument
(e.g., an integer or a name that has a space in it).
Parameters
----------
arg : Cycler
Copy constructor for Cycler (does a shallow copy of iterables).
label : name
The property key. In the 2-arg form of the function,
the label can be any hashable object. In the keyword argument
form of the function, it must be a valid python identifier.
itr : iterable
Finite length iterable of the property values.
Can be a single-property `Cycler` that would
be like a key change, but as a shallow copy.
Returns
-------
cycler : Cycler
New `Cycler` for the given property
"""
if args and kwargs:
raise TypeError(
"cycler() can only accept positional OR keyword arguments -- not both."
)
if len(args) == 1:
if not isinstance(args[0], Cycler):
raise TypeError(
"If only one positional argument given, it must "
"be a Cycler instance."
)
return Cycler(args[0])
elif len(args) == 2:
return _cycler(*args)
elif len(args) > 2:
raise TypeError(
"Only a single Cycler can be accepted as the lone "
"positional argument. Use keyword arguments instead."
)
if kwargs:
return reduce(add, (_cycler(k, v) for k, v in kwargs.items()))
raise TypeError("Must have at least a positional OR keyword arguments")
def _cycler(label: K, itr: Iterable[V]) -> Cycler[K, V]:
"""
Create a new `Cycler` object from a property name and iterable of values.
Parameters
----------
label : hashable
The property key.
itr : iterable
Finite length iterable of the property values.
Returns
-------
cycler : Cycler
New `Cycler` for the given property
"""
if isinstance(itr, Cycler):
keys = itr.keys
if len(keys) != 1:
msg = "Can not create Cycler from a multi-property Cycler"
raise ValueError(msg)
lab = keys.pop()
# Doesn't need to be a new list because
# _from_iter() will be creating that new list anyway.
itr = (v[lab] for v in itr)
return Cycler._from_iter(label, itr)