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Are list-comprehensions and functional functions faster than “for loops”?
In terms of performance in Python, is a list-comprehension, or functions like map() , filter() and reduce() faster than a for loop? Why, technically, they run in a C speed , while the for loop runs in the python virtual machine speed ?.
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Python, creating objects
...r
# Note: I didn't need to create a variable in the class definition before doing this.
student.gpa = float(4.0)
return student
I prefer the former, but there are instances where the latter can be useful – one being when working with document databases like MongoDB.
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Shared-memory objects in multiprocessing
...ther parameters). func with different parameters can be run in parallel. For example:
4 Answers
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C++ Lock-free Hazard Pointer（冒险指针） - C/C++ - 清泛网 - 专注C/C++及内核技术
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// collect in-use pointers
std::unordered_set<T *> in_use;
for (auto p = head_list_.load(std::memory_order_acquire); p; p = p->next_) {
in_use.insert(p->target_);
}
// delete useless pointers
List *retire_head = nullptr;
List *retire_tail = nullptr;
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Import a file from a subdirectory?
...6)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from lib import BoxTime
>>> BoxTime.foo()
foo!
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How do I get the opposite (negation) of a Boolean in Python?
For the following sample:
7 Answers
7
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StringBuilder vs String concatenation in toString() in Java
...it is shorter and the compiler will in fact turn it into version 2 - no performance difference whatsoever.
More importantly given we have only 3
properties it might not make a
difference, but at what point do you
switch from concat to builder?
At the point where you're concatenating in a...
How do I get logs/details of ansible-playbook module executions?
... to ansible-playbook on the command line, you'll see the stdout and stderr for each task executed:
$ ansible-playbook -v playbook.yaml
Ansible also has built-in support for logging. Add the following lines to your ansible configuration file:
[defaults]
log_path=/path/to/logfile
Ansible will l...
PHP function overloading
...() and func_get_arg() to get the arguments passed, and use them normally.
For example:
function myFunc() {
for ($i = 0; $i < func_num_args(); $i++) {
printf("Argument %d: %s\n", $i, func_get_arg($i));
}
}
/*
Argument 0: a
Argument 1: 2
Argument 2: 3.5
*/
myFunc('a', 2, 3.5);
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Batch files - number of command line arguments
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Googling a bit gives you the following result from wikibooks:
set argC=0
for %%x in (%*) do Set /A argC+=1
echo %argC%
Seems like cmd.exe has evolved a bit from the old DOS days :)
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