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cycler.py
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""" 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 (absolute_import, division, print_function, unicode_literals) import six from itertools import product, cycle from six.moves import zip, reduce from operator import mul, add import copy __version__ = '0.10.0' def _process_keys(left, right): """ 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 = next(iter(left)) if left is not None else {} r_peek = next(iter(right)) if right is not None else {} l_key = set(l_peek.keys()) r_key = set(r_peek.keys()) if l_key & r_key: raise ValueError("Can not compose overlapping cycles") return l_key | r_key class Cycler(object): """ 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 : Cycler or None The 'left' cycler right : Cycler or None The 'right' cycler op : func or None Function which composes the 'left' and 'right' cyclers. """ def __call__(self): return cycle(self) def __init__(self, left, right=None, op=None): """Semi-private init Do not use this directly, use `cycler` function instead. """ if isinstance(left, Cycler): self._left = 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 = None if isinstance(right, Cycler): self._right = Cycler(right._left, right._right, right._op) elif right is not None: # Need to copy the dictionary or else that will be a residual # mutable that could lead to strange errors self._right = [copy.copy(v) for v in right] else: self._right = None self._keys = _process_keys(self._left, self._right) self._op = op @property def keys(self): """ The keys this Cycler knows about """ return set(self._keys) def change_key(self, old, new): """ 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("Can't replace %s with %s, %s is already a key" % (old, new, new)) if old not in self._keys: raise KeyError("Can't replace %s with %s, %s is not a key" % (old, new, old)) 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] def _compose(self): """ Compose the 'left' and 'right' components of this cycle with the proper operation (zip or product as of now) """ for a, b in self._op(self._left, self._right): out = dict() out.update(a) out.update(b) yield out @classmethod def _from_iter(cls, label, itr): """ 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 : str The property key. itr : iterable Finite length iterable of the property values. Returns ------- cycler : Cycler New 'base' `Cycler` """ ret = cls(None) ret._left = list({label: v} for v in itr) ret._keys = set([label]) return ret def __getitem__(self, key): # 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 six.iteritems(trans))) else: raise ValueError("Can only use slices with Cycler.__getitem__") def __iter__(self): if self._right is None: return iter(dict(l) for l in self._left) return self._compose() def __add__(self, other): """ Pair-wise combine two equal length cycles (zip) Parameters ---------- other : Cycler The second Cycler """ if len(self) != len(other): raise ValueError("Can only add equal length cycles, " "not {0} and {1}".format(len(self), len(other))) return Cycler(self, other, zip) def __mul__(self, other): """ Outer product of two cycles (`itertools.product`) or integer multiplication. Parameters ---------- other : Cycler or int The second Cycler or integer """ if isinstance(other, Cycler): return Cycler(self, other, product) elif isinstance(other, int): trans = self.by_key() return reduce(add, (_cycler(k, v*other) for k, v in six.iteritems(trans))) else: return NotImplemented def __rmul__(self, other): return self * other def __len__(self): op_dict = {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) def __iadd__(self, other): """ In-place pair-wise combine two equal length cycles (zip) Parameters ---------- other : Cycler The second 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): """ In-place outer product of two cycles (`itertools.product`) Parameters ---------- other : Cycler The second 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): """ Check equality """ 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)) def __repr__(self): op_map = {zip: '+', product: '*'} if self._right is None: lab = self.keys.pop() itr = list(v[lab] for v in self) return "cycler({lab!r}, {itr!r})".format(lab=lab, itr=itr) 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): # 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 += "<th>{key!r}</th>".format(key=key) for d in iter(self): output += "<tr>" for k in sorted_keys: output += "<td>{val!r}</td>".format(val=d[k]) output += "</tr>" output += "</table>" return output def by_key(self): """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 # change this to dict comprehension when drop 2.6 out = dict((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 def simplify(self): """Simplify the Cycler Returned as a composition using only sums (no multiplications) Returns ------- simple : Cycler An equivalent cycler using only summation""" # 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 six.iteritems(trans))) def concat(self, other): """Concatenate this cycler and an other. The keys must match exactly. This returns a single Cycler which is equivalent to `itertools.chain(self, other)` Examples -------- >>> num = cycler('a', range(3)) >>> let = cycler('a', 'abc') >>> num.concat(let) cycler('a', [0, 1, 2, 'a', 'b', 'c']) Parameters ---------- other : `Cycler` The `Cycler` to concatenate to this one. Returns ------- ret : `Cycler` The concatenated `Cycler` """ return concat(self, other) def concat(left, right): """Concatenate two cyclers. The keys must match exactly. This returns a single Cycler which is equivalent to `itertools.chain(left, right)` Examples -------- >>> num = cycler('a', range(3)) >>> let = cycler('a', 'abc') >>> num.concat(let) cycler('a', [0, 1, 2, 'a', 'b', 'c']) Parameters ---------- left, right : `Cycler` The two `Cycler` instances to concatenate Returns ------- ret : `Cycler` The concatenated `Cycler` """ if left.keys != right.keys: msg = '\n\t'.join(["Keys do not match:", "Intersection: {both!r}", "Disjoint: {just_one!r}"]).format( both=left.keys & right.keys, just_one=left.keys ^ right.keys) raise ValueError(msg) _l = left.by_key() _r = right.by_key() return reduce(add, (_cycler(k, _l[k] + _r[k]) for k in left.keys)) 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("cyl() 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 six.iteritems(kwargs))) raise TypeError("Must have at least a positional OR keyword arguments") def _cycler(label, itr): """ 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)