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How to run code when a class is subclassed? [duplicate]
...- Watcher subclasses type, not object. 2 - SuperClass has no superclass at all, not object. I'm just so used to writing down object as a superclass for every class I defined that I somehow missed it that this code was using something else. Although there doesn't seem to be any harm in making SuperCl...
Is there a standard sign function (signum, sgn) in C/C++?
...T val) {
return (T(0) < val) - (val < T(0));
}
Benefits:
Actually implements signum (-1, 0, or 1). Implementations here using copysign only return -1 or 1, which is not signum. Also, some implementations here are returning a float (or T) rather than an int, which seems wasteful.
Works ...
partial string formatting
...he advanced string formatting methods, similar to the string template safe_substitute() function?
21 Answers
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How to keep environment variables when using sudo
...
To allow -E (preserve environment) for wget, you need to specify the SETENV tag on the sudo rule that allows the running of wget -- Example: <username> ALL=(root) NOPASSWD:SETENV: <path to wget>
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Regex Email validation
...ccurate as mine, I thought I would post it here.
@"^[\w!#$%&'*+\-/=?\^_`{|}~]+(\.[\w!#$%&'*+\-/=?\^_`{|}~]+)*"
+ "@"
+ @"((([\-\w]+\.)+[a-zA-Z]{2,4})|(([0-9]{1,3}\.){3}[0-9]{1,3}))$";
For more info go read about it here: C# – Email Regular Expression
Also, this checks for RFC validity ...
What are the “standard unambiguous date” formats for string-to-date conversion in R?
...te (+1). However, the error message "standard unambiguous format" is ironically ambiguous, to which the 23 previous questions attest. A more direct error message like, "format not recognized, see documentation" might improve user experience. Also, I don't believe "01/01/2000" is ISO-8601 ("2000-01-0...
Java Reflection: How to get the name of a variable?
...they are in scope.
Perhaps a byte-code engineering library like ASM would allow you to inspect this information at runtime. The only reasonable place I can think of for needing this information is in a development tool, and so byte-code engineering is likely to be useful for other purposes too.
...
What's the bad magic number error?
...the pyc file or trying to run a pyc from a different version of python (usually later) than your interpreter.
If they are your pyc files, just delete them and let the interpreter re-compile the py files. On UNIX type systems, that could be something as simple as:
rm *.pyc
or:
find . -name '*.py...
Threading pool similar to the multiprocessing Pool?
...
I just found out that there actually is a thread-based Pool interface in the multiprocessing module, however it is hidden somewhat and not properly documented.
It can be imported via
from multiprocessing.pool import ThreadPool
It is implemented using a...
When would anyone use a union? Is it a remnant from the C-only days?
I have learned but don't really get unions. Every C or C++ text I go through introduces them (sometimes in passing), but they tend to give very few practical examples of why or where to use them. When would unions be useful in a modern (or even legacy) case? My only two guesses would be programming ...