8000 Rollaxis always return view by charris · Pull Request #5464 · numpy/numpy · GitHub
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Rollaxis always return view #5464

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Merged
merged 3 commits into from
Jan 19, 2015
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Rollaxis always return view #5464

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5c00d82
DOC : rollaxis returns a view of the input.
jnothman Nov 4, 2014
38b1a7c
ENH: Make rollaxis always return a view.
charris Jan 18, 2015
cf41fce
TST: Tests for numeric.rollaxis.
charris Jan 19, 2015
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ENH: Make rollaxis always return a view. 
Previous to this commit, rollaxis returned a view unless the order of
the axis was unchanged, in which case the input array was returned.
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@charris
charris committed Jan 19, 2015
commit 38b1a7c3038223ee72138413621ef3e00c9224f5
6 changes: 6 additions & 0 deletions doc/release/1.10.0-notes.rst
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Expand Up @@ -50,6 +50,12 @@ the case of matrices. Matrices are special cased for backward
compatibility and still return 1-D arrays as before. If you need to
preserve the matrix subtype, use the methods instead of the functions.

*rollaxis* always returns a view
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Previously, a view was returned except when no change was made in the order
of the axes, in which case the input array was returned. A view is now
returned in all cases.


New Features
============
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17 changes: 11 additions & 6 deletions numpy/core/numeric.py
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Expand Up @@ -1392,6 +1392,7 @@ def roll(a, shift, axis=None):
res = res.reshape(a.shape)
return res


def rollaxis(a, axis, start=0):
"""
Roll the specified axis backwards, until it lies in a given position.
Expand All @@ -1410,7 +1411,9 @@ def rollaxis(a, axis, start=0):
Returns
-------
res : ndarray
A view of `a` with its axes permuted.
For Numpy >= 1.10 a view of `a` is always returned. For earlier
Numpy versions a view of `a` is returned only if the order of the
axes is changed, otherwise the input array is returned.

See Also
--------
Expand All @@ -1436,17 +1439,19 @@ def rollaxis(a, axis, start=0):
msg = 'rollaxis: %s (%d) must be >=0 and < %d'
if not (0 <= axis < n):
raise ValueError(msg % ('axis', axis, n))
if not (0 <= start < n+1):
raise ValueError(msg % ('start', start, n+1))
if (axis < start): # it's been removed
if not (0 <= start < n + 1):
raise ValueError(msg % ('start', start, n + 1))
if (axis < start):
# it's been removed
start -= 1
if axis==start:
return a
if axis == start:
return a[...]
axes = list(range(0, n))
axes.remove(axis)
axes.insert(start, axis)
return a.transpose(axes)


# fix hack in scipy which imports this function
def _move_axis_to_0(a, axis):
return rollaxis(a, axis, 0)
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0