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Fast check for NaN in NumPy
...hine it is about 2.5x faster to use numpy.sum in place of numpy.min:
In [13]: %timeit np.isnan(np.min(x))
1000 loops, best of 3: 244 us per loop
In [14]: %timeit np.isnan(np.sum(x))
10000 loops, best of 3: 97.3 us per loop
Unlike min, sum doesn't require branching, which on modern hardware tends...
std::next_permutation Implementation Explanation
...
Let's look at some permutations:
1 2 3 4
1 2 4 3
1 3 2 4
1 3 4 2
1 4 2 3
1 4 3 2
2 1 3 4
...
How do we go from one permutation to the next? Firstly, let's look at things a little differently. We can view the elements as digits and the permutations as numbers. ...
What does the “yield” keyword do?
...ng its items one by one is called iteration:
>>> mylist = [1, 2, 3]
>>> for i in mylist:
... print(i)
1
2
3
mylist is an iterable. When you use a list comprehension, you create a list, and so an iterable:
>>> mylist = [x*x for x in range(3)]
>>> for i in my...
How do I find the duplicates in a list and create another list with them?
...
34 Answers
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How do I check if a string is unicode or ascii?
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301
In Python 3, all strings are sequences of Unicode characters. There is a bytes type that holds...
What are the mathematical/computational principles behind this game?
...nd you have the question:
Can we have a geometry with just 2 points? With 3 points? With 4? With 7?
There are still open questions regarding this problem but we do know this:
If there are geometries with Q points, then Q = n^2 + n + 1 and n is called the order of the geometry.
There are n+1 poin...
How to insert newline in string literal?
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323
Well, simple options are:
string.Format:
string x = string.Format("first line{0}second line...
Using async/await for multiple tasks
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int[] ids = new[] { 1, 2, 3, 4, 5 };
Parallel.ForEach(ids, i => DoSomething(1, i, blogClient).Wait());
Although you run the operations in parallel with the above code, this code blocks each thread that each operation runs on. For example, if the ...
Pandas dataframe get first row of each group
...;> df.groupby('id').first()
value
id
1 first
2 first
3 first
4 second
5 first
6 first
7 fourth
If you need id as column:
>>> df.groupby('id').first().reset_index()
id value
0 1 first
1 2 first
2 3 first
3 4 second
4 5 first
5 6...
“Unicode Error ”unicodeescape" codec can't decode bytes… Cannot open text files in Python 3 [duplica
I am using python 3.1, on a windows 7 machines. Russian is the default system language, and utf-8 is the default encoding.
...