example-code-2e/02-array-seq/memoryviews.ipynb

memoryviews¶

References¶

• PEP-3118 Revising the buffer protocol (2006)
• issue14130 memoryview: add multi-dimensional indexing and slicing (2012)

In [1]:

import sys
print(sys.version)

3.7.1 (default, Dec 14 2018, 13:28:58) 
[Clang 4.0.1 (tags/RELEASE_401/final)]

In [2]:

mv1d = memoryview(bytes(range(35, 50)))
mv1d

Out[2]:

<memory at 0x1045a31c8>

In [3]:

list(mv1d)

Out[3]:

[35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49]

In [4]:

mv2d = mv1d.cast('B', [3, 5])
mv2d

Out[4]:

<memory at 0x10464a120>

In [5]:

mv2d.shape

Out[5]:

(3, 5)

In [6]:

len(mv2d)

Out[6]:

3

In [7]:

mv2d.tolist()

Out[7]:

[[35, 36, 37, 38, 39], [40, 41, 42, 43, 44], [45, 46, 47, 48, 49]]

In [8]:

for row in mv2d.tolist():
    print(row)

[35, 36, 37, 38, 39]
[40, 41, 42, 43, 44]
[45, 46, 47, 48, 49]

In [9]:

mv2d[1, 2]

Out[9]:

42

In [10]:

mv2d.tolist()[1][2]

Out[10]:

42