def interpose(el, seq):
""" Introduce element between each pair of elements in seq
>>> list(interpose("a", [1, 2, 3]))
[1, 'a', 2, 'a', 3]
"""
inposed = concat(zip(itertools.repeat(el), seq))
next(inposed)
return inposed
def keymap(func, d, factory=dict):
""" Apply function to keys of dictionary
>>> bills = {"Alice": [20, 15, 30], "Bob": [10, 35]}
>>> keymap(str.lower, bills) # doctest: +SKIP
{'alice': [20, 15, 30], 'bob': [10, 35]}
See Also:
valmap
itemmap
"""
rv = factory()
rv.update(zip(map(func, iterkeys(d)), itervalues(d)))
return rv
def valmap(func, d, factory=dict):
""" Apply function to values of dictionary
>>> bills = {"Alice": [20, 15, 30], "Bob": [10, 35]}
>>> valmap(sum, bills) # doctest: +SKIP
{'Alice': 65, 'Bob': 45}
See Also:
keymap
itemmap
"""
rv = factory()
rv.update(zip(iterkeys(d), map(func, itervalues(d))))
return rv
def sliding_window(n, seq):
""" A sequence of overlapping subsequences
>>> list(sliding_window(2, [1, 2, 3, 4]))
[(1, 2), (2, 3), (3, 4)]
This function creates a sliding window suitable for transformations like
sliding means / smoothing
>>> mean = lambda seq: float(sum(seq)) / len(seq)
>>> list(map(mean, sliding_window(2, [1, 2, 3, 4])))
[1.5, 2.5, 3.5]
"""
return zip(*(collections.deque(itertools.islice(it, i), 0) or it
for i, it in enumerate(itertools.tee(seq, n))))
def diff(*seqs, **kwargs):
""" Return those items that differ between sequences
>>> list(diff([1, 2, 3], [1, 2, 10, 100]))
[(3, 10)]
Shorter sequences may be padded with a ``default`` value:
>>> list(diff([1, 2, 3], [1, 2, 10, 100], default=None))
[(3, 10), (None, 100)]
A ``key`` function may also be applied to each item to use during
comparisons:
>>> list(diff(['apples', 'bananas'], ['Apples', 'Oranges'], key=str.lower))
[('bananas', 'Oranges')]
"""
N = len(seqs)
if N == 1 and isinstance(seqs[0], list):
seqs = seqs[0]
N = len(seqs)
if N < 2:
raise TypeError('Too few sequences given (min 2 required)')
default = kwargs.get('default', no_default)
if default == no_default:
iters = zip(*seqs)
else:
iters = zip_longest(*seqs, fillvalue=default)
key = kwargs.get('key', None)
if key is None:
for items in iters:
if items.count(items[0]) != N:
yield items
else:
for items in iters:
vals = tuple(map(key, items))
if vals.count(vals[0]) != N:
yield items
def partition(n, seq, pad=no_pad):
""" Partition sequence into tuples of length n
>>> list(partition(2, [1, 2, 3, 4]))
[(1, 2), (3, 4)]
If the length of ``seq`` is not evenly divisible by ``n``, the final tuple
is dropped if ``pad`` is not specified, or filled to length ``n`` by pad:
>>> list(partition(2, [1, 2, 3, 4, 5]))
[(1, 2), (3, 4)]
>>> list(partition(2, [1, 2, 3, 4, 5], pad=None))
[(1, 2), (3, 4), (5, None)]
See Also:
partition_all
"""
args = [iter(seq)] * n
if pad is no_pad:
return zip(*args)
else:
return zip_longest(*args, fillvalue=pad)