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[3.12] Add reshape() recipe to demonstrate a use case for batched() and chained.from_iterable() (gh-113198) #113201

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Dec 16, 2023
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[3.12] Add reshape() recipe to demonstrate a use case for batched() and chained.from_iterable() (gh-113198) #113201

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27 changes: 24 additions & 3 deletions Doc/library/itertools.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1036,10 +1036,15 @@ The following recipes have a more mathematical flavor:
# sum_of_squares([10, 20, 30]) -> 1400
return math.sumprod(*tee(it))

def transpose(it):
"Swap the rows and columns of the input."
def reshape(matrix, cols):
"Reshape a 2-D matrix to have a given number of columns."
# reshape([(0, 1), (2, 3), (4, 5)], 3) --> (0, 1, 2), (3, 4, 5)
return batched(chain.from_iterable(matrix), cols)

def transpose(matrix):
"Swap the rows and columns of a 2-D matrix."
# transpose([(1, 2, 3), (11, 22, 33)]) --> (1, 11) (2, 22) (3, 33)
return zip(*it, strict=True)
return zip(*matrix, strict=True)

def matmul(m1, m2):
"Multiply two matrices."
Expand Down Expand Up @@ -1254,6 +1259,22 @@ The following recipes have a more mathematical flavor:
>>> sum_of_squares([10, 20, 30])
1400

>>> list(reshape([(0, 1), (2, 3), (4, 5)], 3))
[(0, 1, 2), (3, 4, 5)]
>>> M = [(0, 1, 2, 3), (4, 5, 6, 7), (8, 9, 10, 11)]
>>> list(reshape(M, 1))
[(0,), (1,), (2,), (3,), (4,), (5,), (6,), (7,), (8,), (9,), (10,), (11,)]
>>> list(reshape(M, 2))
[(0, 1), (2, 3), (4, 5), (6, 7), (8, 9), (10, 11)]
>>> list(reshape(M, 3))
[(0, 1, 2), (3, 4, 5), (6, 7, 8), (9, 10, 11)]
>>> list(reshape(M, 4))
[(0, 1, 2, 3), (4, 5, 6, 7), (8, 9, 10, 11)]
>>> list(reshape(M, 6))
[(0, 1, 2, 3, 4, 5), (6, 7, 8, 9, 10, 11)]
>>> list(reshape(M, 12))
[(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11)]

>>> list(transpose([(1, 2, 3), (11, 22, 33)]))
[(1, 11), (2, 22), (3, 33)]

Expand Down
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