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Prepend a level to a pandas MultiIndex
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A nice way to do this in one line using pandas.concat():
import pandas as pd
pd.concat([df], keys=['Foo'], names=['Firstlevel'])
An even shorter way:
pd.concat({'Foo': df}, names=['Firstlevel'])
This can be generalized to many data frames, see the docs.
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SQL Server Management Studio SSMS tries to “save to file” instead of execute on F5
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From the Query Menu -> Results To ->
Results To Grid.
OR
Press Ctrl + D
Once you have tried one of the steps above, run your query again by pressing F5.
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How to remove last n characters from every element in the R vector
... online of how to remove the last n characters from every element of a vector (array?)
5 Answers
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Validating IPv4 addresses with regexp
I've been trying to get an efficient regex for IPv4 validation, but without much luck. It seemed at one point I had had it with (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?(\.|$)){4} , but it produces some strange results:
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How to send commands when opening a tmux session inside another tmux session?
...new-window) in a second-level instance of tmux, you would type C-b C-b c. For a third-level instance of tmux you would type C-b C-b C-b C-b c.
This doubling for each level can be annoying if you are commonly dealing with multiple layers of tmux. If you can spare some other key, you could make a non...
How to return an NSMutableArray from an NSSet
...SMutableArray *array = [NSMutableArray arrayWithArray:[set allObjects]];
Or, alternatively, if you want to handle the object ownership:
NSMutableArray *array = [[set allObjects] mutableCopy];
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Get all keys of an NSDictionary as an NSArray
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the order of keys returned by allKeys is undefined... so allKeys.firstObject or allKeys][0] is dangerous either way
– Brad Thomas
Feb 24 '17 at 19:39
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Scala: Nil vs List()
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374527572
scala> System.identityHashCode(List())
374527572
Nil is more idiomatic and can be preferred in most cases.
Questions?
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Cluster analysis in R: determine the optimal number of clusters
...subset of below data, how many clusters will be appropriate? How can I perform cluster dendro analysis?
7 Answers
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Creating a daemon in Linux
In Linux I want to add a daemon that cannot be stopped and which monitors filesystem changes.
If any changes are detected, it should write the path to the console where it was started plus a newline.
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