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How to store a command in a variable in a shell script?
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Use eval:
x="ls | wc"
eval "$x"
y=$(eval "$x")
echo "$y"
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How to install a previous exact version of a NPM package?
...ckage, just specify it
npm install <package>@<version>
For example: npm install express@3.0.0
You can also add the --save flag to that command to add it to your package.json dependencies, or --save --save-exact flags if you want that exact version specified in your package.json depen...
What is the best way to repeatedly execute a function every x seconds?
I want to repeatedly execute a function in Python every 60 seconds forever (just like an NSTimer in Objective C). This code will run as a daemon and is effectively like calling the python script every minute using a cron, but without requiring that to be set up by the user.
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Convert a number range to another range, maintaining ratio
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NewValue = (((OldValue - OldMin) * (NewMax - NewMin)) / (OldMax - OldMin)) + NewMin
Or a little more readable:
OldRange = (OldMax - OldMin)
NewRange = (NewMax - NewMin)
NewValue = (((OldValue - OldMin) * NewRange) / OldRange) + NewMin
Or if you want to pr...
Is there a builtin identity function in python?
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advantage: takes any number of parameters
disadvantage: the result is a boxed version of the parameters
OR
_ = lambda x: x
advantage: doesn't change the type of the parameter
disadvantage: takes exactly 1 positional parameter
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How does tuple comparison work in Python?
... been reading the Core Python programming book, and the author shows an example like:
4 Answers
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Using global variables in a function
...ants to make sure that you really know that's what you're playing with by explicitly requiring the global keyword.
See other answers if you want to share a global variable across modules.
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C++: Rounding up to the nearest multiple of a number
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adding noise to a signal in python
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In some contexts, it might make more sense to multiply your signal by a noise array (centered around 1), rather than adding a noise array, but of course that depends on the nature of the noise that you're trying to simulate.
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Bulk insert with SQLAlchemy ORM
...e a huge difference in performance on the server side resulting in about 10x more inserts/s. Apparently is bulk-loading using \copy (or COPY on the server) using a packing in communicating from client-to-server a LOT better than using SQL via SQLAlchemy. More info: Large bulk insert performance diff...