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Why does the order of the loops affect performance when iterating over a 2D array?
...mensional. So while you imagine your array like this:
0,0 | 0,1 | 0,2 | 0,3
----+-----+-----+----
1,0 | 1,1 | 1,2 | 1,3
----+-----+-----+----
2,0 | 2,1 | 2,2 | 2,3
Your computer stores it in memory as a single line:
0,0 | 0,1 | 0,2 | 0,3 | 1,0 | 1,1 | 1,2 | 1,3 | 2,0 | 2,1 | 2,2 | 2,3
In the 2...
What is a good regular expression to match a URL? [duplicate]
...[-a-zA-Z0-9()@:%_\+.~#?&//=]*)
To try this out see http://regexr.com?37i6s, or for a version which is less restrictive http://regexr.com/3e6m0.
Example JavaScript implementation:
var expression = /[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)?/gi;...
How can I force division to be floating point? Division keeps rounding down to 0?
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In Python 2, division of two ints produces an int. In Python 3, it produces a float. We can get the new behaviour by importing from __future__.
>>> from __future__ import division
>>> a = 4
>>> b = 6
>>> c = a / b
>>> c
0.66666666666666663
...
Pandas - How to flatten a hierarchical index in columns
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edited Jan 17 '14 at 19:36
answered Jan 24 '13 at 18:37
A...
How do I convert a numpy array to (and display) an image?
...IL import Image
import numpy as np
w, h = 512, 512
data = np.zeros((h, w, 3), dtype=np.uint8)
data[0:256, 0:256] = [255, 0, 0] # red patch in upper left
img = Image.fromarray(data, 'RGB')
img.save('my.png')
img.show()
shar...
Getting key with maximum value in dictionary?
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632
You can use operator.itemgetter for that:
import operator
stats = {'a':1000, 'b':3000, 'c': 10...
Why isn't my Pandas 'apply' function referencing multiple columns working? [closed]
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381
Seems you forgot the '' of your string.
In [43]: df['Value'] = df.apply(lambda row: my_test(r...
How to check whether a pandas DataFrame is empty?
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edited Dec 15 '17 at 17:37
Dave Thomas
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Finding duplicates in O(n) time and O(1) space
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Simple way to create matrix of random numbers
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