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Is it more efficient to copy a vector by reserving and copying, or by creating and swapping? [duplic
I am trying to efficiently make a copy of a vector. I see two possible approaches:
7 Answers
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Removing multiple keys from a dictionary safely
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Why not like this:
entries = ('a', 'b', 'c')
the_dict = {'b': 'foo'}
def entries_to_remove(entries, the_dict):
for key in entries:
if key in the_dict:
del the_dict[key]
A more compact version was provided by mattbornski using dict.pop...
How can the Euclidean distance be calculated with NumPy?
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Use numpy.linalg.norm:
dist = numpy.linalg.norm(a-b)
You can find the theory behind this in Introduction to Data Mining
This works because Euclidean distance is l2 norm and the default value of ord parameter in numpy.linalg.norm is 2.
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C++, variable declaration in 'if' expression
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As of C++17 what you were trying to do is finally possible:
if (int a = Func1(), b = Func2(); a && b)
{
// Do stuff with a and b.
}
Note the use of ; of instead of , to separate the declaration and the actual condition.
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pandas read_csv and filter columns with usecols
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The answer by @chip completely misses the point of two keyword arguments.
names is only necessary when there is no header and you want to specify other arguments using column names rather than integer indices.
usecols is supposed to p...
Error in finding last used cell in Excel with VBA
...the last row. This will also cover the best practices to follow when finding the last row. And hence I will keep on updating it whenever I come across a new scenario/information.
Unreliable ways of finding the last row
Some of the most common ways of finding last row which are highly unreliable ...
Why is `std::move` named `std::move`?
...mes confuses people. However the intent of this naming is not to confuse, but rather to make your code more readable.
The history of move dates back to the original move proposal in 2002. This paper first introduces the rvalue reference, and then shows how to write a more efficient std::swap:
te...
Add column with number of days between dates in DataFrame pandas
I want to subtract dates in 'A' from dates in 'B' and add a new column with the difference.
4 Answers
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C++11 rvalues and move semantics confusion (return statement)
... = return_vector();
The first example returns a temporary which is caught by rval_ref. That temporary will have its life extended beyond the rval_ref definition and you can use it as if you had caught it by value. This is very similar to the following:
const std::vector<int>& rval_ref = ...
How to do case insensitive string comparison?
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The simplest way to do it (if you're not worried about special Unicode characters) is to call toUpperCase:
var areEqual = string1.toUpperCase() === string2.toUpperCase();
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