2024-heraklion-data/exercises/.ipynb_checkpoints/view_or_copy-checkpoint.ipynb at 8420e30651780c51e6395f8e7faa535d64582c9b

In [107]:

import numpy as np


def is_view(a):
    return a.base is not None


def print_info(a):
    txt = f"""
Is it a view? {is_view(a)}

dtype\t{a.dtype}
ndim\t{a.ndim}
shape\t{a.shape}
strides\t{a.strides}
    """
    print(a)
    print(txt)


x = np.arange(12).reshape(3, 4).copy()
print_info(x)

[[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]]

Is it a view? False

dtype	int64
ndim	2
shape	(3, 4)
strides	(32, 8)

In [108]:

y = x[::2, :]
print_info(y)

[[ 0  1  2  3]
 [ 8  9 10 11]]

Is it a view? True

dtype	int64
ndim	2
shape	(2, 4)
strides	(64, 8)

In [109]:

y = x[1, :]
print_info(y)

[4 5 6 7]

Is it a view? True

dtype	int64
ndim	1
shape	(4,)
strides	(8,)

In [110]:

y = x[1]
print_info(y)

[4 5 6 7]

Is it a view? True

dtype	int64
ndim	1
shape	(4,)
strides	(8,)

In [111]:

y = x[[1, 2], [0, 3]]
print_info(y)

[ 4 11]

Is it a view? False

dtype	int64
ndim	1
shape	(2,)
strides	(8,)

In [112]:

# Get the first and third row
y = x[[0, 2], :]
print_info(y)

[[ 0  1  2  3]
 [ 8  9 10 11]]

Is it a view? False

dtype	int64
ndim	2
shape	(2, 4)
strides	(32, 8)

In [113]:

y = x + 2
print_info(y)

[[ 2  3  4  5]
 [ 6  7  8  9]
 [10 11 12 13]]

Is it a view? False

dtype	int64
ndim	2
shape	(3, 4)
strides	(32, 8)

In [114]:

y = x[[1, 2, 0], [1, 1, 2]]
print_info(y)

[5 9 2]

Is it a view? False

dtype	int64
ndim	1
shape	(3,)
strides	(8,)

In [115]:

y = x.reshape((6, 2))
print_info(y)

[[ 0  1]
 [ 2  3]
 [ 4  5]
 [ 6  7]
 [ 8  9]
 [10 11]]

Is it a view? True

dtype	int64
ndim	2
shape	(6, 2)
strides	(16, 8)

In [116]:

y = x.T.reshape((6, 2))
print_info(y)

[[ 0  4]
 [ 8  1]
 [ 5  9]
 [ 2  6]
 [10  3]
 [ 7 11]]

Is it a view? True

dtype	int64
ndim	2
shape	(6, 2)
strides	(16, 8)

In [117]:

y = x.ravel()
print_info(y)

[ 0  1  2  3  4  5  6  7  8  9 10 11]

Is it a view? True

dtype	int64
ndim	1
shape	(12,)
strides	(8,)

In [118]:

y = x.T.ravel()
print_info(y)

[ 0  4  8  1  5  9  2  6 10  3  7 11]

Is it a view? False

dtype	int64
ndim	1
shape	(12,)
strides	(8,)

In [119]:

y = x[(x % 2) == 0]
print_info(y)

[ 0  2  4  6  8 10]

Is it a view? False

dtype	int64
ndim	1
shape	(6,)
strides	(8,)

In [120]:

y = np.sort(x, axis=1)
print_info(y)

[[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]]

Is it a view? False

dtype	int64
ndim	2
shape	(3, 4)
strides	(32, 8)

In [ ]:

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