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How do you rotate a two dimensional array?
...trix):
size = len(matrix)
layer_count = size / 2
for layer in range(0, layer_count):
first = layer
last = size - first - 1
print 'Layer %d: first: %d, last: %d' % (layer, first, last)
# 5x5 matrix
matrix = [
[ 0, 1, 2, 3, 4],
[ 5, 6, 6, 8, 9],
[10,11...
Add missing dates to pandas dataframe
...
You could use Series.reindex:
import pandas as pd
idx = pd.date_range('09-01-2013', '09-30-2013')
s = pd.Series({'09-02-2013': 2,
'09-03-2013': 10,
'09-06-2013': 5,
'09-07-2013': 1})
s.index = pd.DatetimeIndex(s.index)
s = s.reindex(idx, fill...
Sorting a vector of custom objects
...
Sorting such a vector or any other applicable (mutable input iterator) range of custom objects of type X can be achieved using various methods, especially including the use of standard library algorithms like
sort,
stable_sort,
partial_sort or
partial_sort_copy.
Since most of the techniqu...
The tilde operator in C
...gned->signed), partly because the possible unsigned values span a wider range than can be crammed into a signed variable, and partly because that problem is not well-defined without specifying -from outside information probably- what sign to invent. Your two comments got different replies because...
What is the advantage to using bloom filters?
...is that you can have only one filter (you check whether the combination of user_id + article_id is there)
bitcoin uses bloom filter for wallet synchronization
Akamai's web servers use Bloom filters to prevent "one-hit-wonders" from being stored in its disk caches. One-hit-wonders are web objects req...
Convert light frequency to RGB?
...he important point that some colours are not representable in RGB (bright oranges being a good example) because you cannot "make" arbitrary colours of light by adding three primary colours together, whatever our physics teachers may have told us (well mine did). Too bad, but in practice not usually ...
vertical & horizontal lines in matplotlib
...alling, axhline() and axvline() draw lines that span a portion of the axis range, regardless of coordinates. The parameters xmin or ymin use value 0.0 as the minimum of the axis and 1.0 as the maximum of the axis.
Instead, use plt.plot((x1, x2), (y1, y2), 'k-') to draw a line from the point (x1, y1...
How can I convert an RGB image into grayscale in Python?
... seconds
sk : 2.120 seconds
PIL and SciPy gave identical numpy arrays (ranging from 0 to 255). SkImage gives arrays from 0 to 1. In addition the colors are converted slightly different, see the example from the CUB-200 dataset.
SkImage:
PIL :
SciPy :
Original:
Diff :
Code
...
How to change the name of a Django app?
...ault path is <app_label>/<model_name>_<suffix>.html)
Run raw SQL to fix migrations and content_types app (unfortunately, some raw SQL is unavoidable). You can not run this in a migration.
UPDATE django_migrations
SET app = 'catalogue'
WHERE app = 'shop';
UPDATE django_content...
Understanding REST: Verbs, error codes, and authentication
...e resource is "the user". You would need a PUT to http://example.com/users/USER_ID with the old and new passwords in the body. You are acting on "the user" resource, and a change password is simply an update request. It's quite similar to the UPDATE statement in a relational database.
My instinc...