10000 MAINT: Simplify block implementation by j-towns · Pull Request #9667 · numpy/numpy · GitHub
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MAINT: Simplify block implementation #9667

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Merged
merged 23 commits into from
Nov 12, 2017
Merged

MAINT: Simplify block implementation #9667

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a5c6f0d
Simplify block implementation
j-towns Sep 7, 2017
2dcc9aa
np.block style improvements
j-towns Sep 7, 2017
e787a9f
Reflect asanyarray behaviour in block
j-towns Sep 8, 2017
95adb77
Add empty list comment to block depth check
j-towns Sep 10, 2017
07a3f43
Use strict type checking (not isinstance)
j-towns Sep 11, 2017
19fc68c
Re-add tuple type-check comment
j-towns Sep 11, 2017
997ac2c
Re-add `atleast_nd` function.
j-towns Sep 11, 2017
7eb1044
Add detailed comment to _block_check_depths_match
j-towns Sep 18, 2017
ff7f726
Extend comments _block_check_depths_match
j-towns Sep 20, 2017
6ecd2b4
Try not recomputing list_ndim
j-towns Sep 23, 2017
1211b70
Slight simplification to logic
j-towns Sep 25, 2017
8000 ffa6cf6
Add two tests for different arr_ndims
j-towns Sep 25, 2017
3ed6936
Simplify further - matching docstring logic
j-towns Sep 25, 2017
5f9f1fa
Rename list_ndim to max_depth
j-towns Sep 25, 2017
8a83a5f
rm extra line from near top of shape_base
j-towns Sep 25, 2017
5a0557a
Pre-calculate max array ndim
j-towns Oct 12, 2017
c2b5be5
Further slight simplifications
j-towns Oct 12, 2017
bd6729d
Update block docstrings
j-towns Oct 12, 2017
ad278f3
Fix python 3.4 sequence error
j-towns Oct 12, 2017
2c1734b
Correct empty list ndim
j-towns Oct 26, 2017
eaddf39
Avoid using zip(*...) syntax
j-towns Nov 1, 2017
a5cbc93
Use builtin next method
j-towns Nov 1, 2017
a691f2d
Rm unnecessary enumerate
j-towns Nov 9, 2017
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Update block docstrings
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@j-towns
j-towns committed Oct 12, 2017
commit bd6729d0d1a6004360f44524a477524ccdc96f17
18 changes: 14 additions & 4 deletions numpy/core/shape_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -378,9 +378,12 @@ def _block_check_depths_match(arrays, parent_index=[]):
The parameter `parent_index` is the full index of `arrays` within the
nested lists passed to _block_check_depths_match at the top of the
recursion.
The return value is the full index of an element (specifically the
first element) from the bottom of the nesting in `arrays`. An empty
list at the bottom of the nesting is represented by a `None` index.
The return value is a pair. The first item returned is the full index
of an element (specifically the first element) from the bottom of the
nesting in `arrays`. An empty list at the bottom of the nesting is
represented by a `None` index.
The second item is the maximum of the ndims of the arrays nested in
`arrays`.
"""
def format_index(index):
idx_str = ''.join('[{}]'.format(i) for i in index if i is not None)
Expand Down Expand Up @@ -423,6 +426,13 @@ def format_index(index):


def _block(arrays, max_depth, result_ndim):
"""
Internal implementation of block. `arrays` is the argument passed to
block. `max_depth` is the depth of nested lists within `arrays` and
`result_ndim` is the greatest of the dimensions of the arrays in
`arrays` and the depth of the lists in `arrays` (see block docstring
for details).
"""
def atleast_nd(a, ndim):
# Ensures `a` has at least `ndim` dimensions by prepending
# ones to `a.shape` as necessary
Expand All @@ -436,7 +446,7 @@ def block_recursion(arrays, depth=0):
return _nx.concatenate(arrs, axis=-(max_depth-depth))
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This now reflects the wording of the docstring quite closely:

Blocks in the innermost lists are concatenated (see `concatenate`) along
the last dimension (-1), then these are concatenated along the
second-last dimension (-2), and so on until the outermost list is reached.

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Wouldn't -(max_depth-depth) just be (depth-max_depth)?

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Also slight personal preference to having spaces around binary operators for readability.

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@j-towns j-towns Oct 31, 2017 •
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Wouldn't -(max_depth-depth) just be (depth-max_depth)?

It would, yeah. The reason I wrote it that way round was because I wanted to match the docstring as closely as possible (my original motivation for this pr was to make it a bit clearer to people reading the code how block actually worked). The docstring says:

Blocks in the innermost lists are concatenated (see concatenate) along the last dimension (-1), then these are concatenated along the second-last dimension (-2), and so on until the outermost list is reached.

To me the correspondence between the docstring and the code is ever-so-slightly clearer with the expression the way round that it currently is, and I think the effect on performance is probably negligable.

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Also slight personal preference to having spaces around binary operators for readability.

I often instinctively shorten things when they're being fed to a keyword argument, because you don't normally put spaces around the = sign. Don't

axis=-(max_depth - depth)

and

axis=depth - max_depth

look a bit weird?

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The style point is minor. Though there are many tools (e.g. flake8) that consider not having spaces around binary operators an error regardless of context. Normally this is argued from the standpoint of readability (including in PEP8 when it was introduced). Hence why I mentioned it. Adding parentheses around the keyword argument's value help guide the eye when following these style tools' recommendations. Not strongly attached to this styling nit though.

else:
# We've 'bottomed out' - arrays is either a scalar or an array
# depth == max_depth
# type(arrays) is not list
return atleast_nd(arrays, result_ndim)

return block_recursion(arrays)
Expand Down
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