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Append values to a set in Python
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420
keep.update(yoursequenceofvalues)
e.g, keep.update(xrange(11)) for your specific example. O...
Removing viewcontrollers from navigation stack
...vigation stack, with say 5 UIViewControllers. I want to remove the 3rd and 4th viewcontrollers in the stack on the click of a button in the 5th viewcontroller. Is it possible to do this? If so how?
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error: command 'gcc' failed with exit status 1 while installing eventlet
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374
Your install is failing because you don't have the python development headers installed. You can...
Finding the average of a list
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On Python 3.4+ you can use statistics.mean()
l = [15, 18, 2, 36, 12, 78, 5, 6, 9]
import statistics
statistics.mean(l) # 20.11111111111111
On older versions of Python you can do
sum(l) / len(l)
On Python 2 you need to convert len...
How does facebook, gmail send the real time notification?
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430
The way Facebook does this is pretty interesting.
A common method of doing such notification...
Relative frequencies / proportions with dplyr
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mutate(freq = n / sum(n))
# am gear n freq
# 1 0 3 15 0.7894737
# 2 0 4 4 0.2105263
# 3 1 4 8 0.6153846
# 4 1 5 5 0.3846154
From the dplyr vignette:
When you group by multiple variables, each summary peels off one level of the grouping. That makes it easy to prog...
Find indices of elements equal to zero in a NumPy array
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numpy.where() is my favorite.
>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8])
>>> numpy.where(x == 0)[0]
array([1, 3, 5])
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Traits vs. interfaces
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240
An interface defines a set of methods that the implementing class must implement.
When a trait...