From 77fde8dc16dc808b9f9838af1aa1253e15cab6ad Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Fri, 25 Dec 2020 16:43:20 -0800 Subject: Add convolve() to the itertools recipes (GH-23928) --- Doc/library/itertools.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index 612a66f..03416a0 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -786,6 +786,18 @@ which incur interpreter overhead. def dotproduct(vec1, vec2): return sum(map(operator.mul, vec1, vec2)) + def convolve(signal, kernel): + # See: https://betterexplained.com/articles/intuitive-convolution/ + # convolve(data, [0.25, 0.25, 0.25, 0.25]) --> Moving average (blur) + # convolve(data, [1, -1]) --> 1st finite difference (1st derivative) + # convolve(data, [1, -2, 1]) --> 2nd finite difference (2nd derivative) + kernel = list(reversed(kernel)) + n = len(kernel) + window = collections.deque([0] * n, maxlen=n) + for x in chain(signal, repeat(0, n-1)): + window.append(x) + yield sum(map(operator.mul, kernel, window)) + def flatten(list_of_lists): "Flatten one level of nesting" return chain.from_iterable(list_of_lists) -- cgit v0.12