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Pandas - How to flatten a hierarchical index in columns
...e a data frame with a hierarchical index in axis 1 (columns) (from a groupby.agg operation):
17 Answers
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How do exceptions work (behind the scenes) in c++
I keep seeing people say that exceptions are slow, but I never see any proof. So, instead of asking if they are, I will ask how do exceptions work behind the scenes, so I can make decisions of when to use them and whether they are slow.
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postgresql list and order tables by size
How can I list all the tables of a PostgreSQL database and order them by size ?
7 Answers
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How to write a foreach in SQL Server?
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You seem to want to use a CURSOR. Though most of the times it's best to use a set based solution, there are some times where a CURSOR is the best solution. Without knowing more about your real problem, we can't help you more than that:
DECLARE @PractitionerId int
DECLARE MY_CURSOR CURSO...
What is the best way to convert an array to a hash in Ruby
In Ruby, given an array in one of the following forms...
11 Answers
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Filtering for empty or NULL names in a queryset
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You could do this:
Name.objects.exclude(alias__isnull=True)
If you need to exclude null values and empty strings, the preferred way to do so is to chain together the conditions like so:
Name.objects.exclude(alias__isnull=True).exclude(alias__exact...
What is the difference between a.getClass() and A.class in Java?
...xist surrounding the choice to use a.getClass() or A.class ? Either can be used wherever a Class<?> is expected, but I imagine that there would be performance or other subtle benefits to using both in different circumstances (just like there are with Class.forName() and ClassLoader.loa...
Rename a git submodule
Is there some easy way to rename a git submodule directory (other than going through the entire motion of deleting it and re-adding it with a new destination name).
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Difference between HashMap, LinkedHashMap and TreeMap
What is the difference between HashMap , LinkedHashMap and TreeMap in Java?
I don't see any difference in the output as all the three has keySet and values . What are Hashtable s?
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Can grep show only words that match search pattern?
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edited Feb 5 '16 at 7:43
Stefan van den Akker
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