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Does SQLAlchemy have an equivalent of Django's get_or_create?
...odel, defaults=None, **kwargs):
instance = session.query(model).filter_by(**kwargs).first()
if instance:
return instance, False
else:
params = dict((k, v) for k, v in kwargs.iteritems() if not isinstance(v, ClauseElement))
params.update(defaults or {})
ins...
When should one use a spinlock instead of mutex?
...il being woken up, which will be the case once the mutex is being unlocked by whatever thread was holding the lock before. When a thread tries to lock a spinlock and it does not succeed, it will continuously re-try locking it, until it finally succeeds; thus it will not allow another thread to take ...
Can git undo a checkout of unstaged files
... yet added (staged), it is purely "private".
Meaning it cannot be restored by GIT if overwritten with the index or the HEAD version (unless you have a copy of your current work somewhere).
A "private" content is one only visible in your current directory, but not registered in any way in Git.
Note: ...
When to use ' (or quote) in Lisp?
...
Short answer
Bypass the default evaluation rules and do not evaluate the expression (symbol or s-exp), passing it along to the function exactly as typed.
Long Answer: The Default Evaluation Rule
When a regular (I'll come to that later) ...
Efficient way to return a std::vector in c++
...1, this is the preferred way:
std::vector<X> f();
That is, return by value.
With C++11, std::vector has move-semantics, which means the local vector declared in your function will be moved on return and in some cases even the move can be elided by the compiler.
...
pycharm running way slow
I'm a big fan of PyCharm by JetBrains but I do run into some issues that I thought maybe I'll ask here about.
9 Answers
...
How does git compute file hashes?
The SHA1 hashes stored in the tree objects (as returned by git ls-tree ) do not match the SHA1 hashes of the file content (as returned by sha1sum )
...
How to profile a bash shell script slow startup?
.... Change the setting of PS4:
PS4='+ $EPOCHREALTIME\011 '
As pointed out by @pawamoy, you can use BASH_XTRACEFD to send the output of the trace to a separate file descriptor if you have Bash 4.1 or later. From this answer:
#!/bin/bash
exec 5> command.txt
BASH_XTRACEFD="5"
echo -n "hello "
s...
Is there a way for multiple processes to share a listening socket?
...arent/child processes need to work out which handle needs to be duplicated by some IPC mechanism (although this could be as simple as a file in the filesystem)
CLARIFICATION:
In answer to the OP's original question, no, multiple processes cannot bind(); just the original parent process would call ...
What is the difference between “Class.forName()” and “Class.forName().newInstance()”?
...alling clazz.newInstance() creates a new instance of the class represented by this Class object. The class is instantiated as if by a new expression with an empty argument list. In other words, this is here actually equivalent to a new Demo() and returns a new instance of Demo.
And running this De...