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What do all of Scala's symbolic operators mean?
... // Syntactic sugar/composition or common method
<= // Common method
_._ // Typo, though it's probably based on Keyword/composition
:: // Common method
:+= // Common method
The exact meaning of most of these methods depend on the class that is defining them. For example, <= on Int ...
理解Python的 with 语句 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...hat the statement after with has to evaluate an object that responds to an __enter__() as well as an __exit__() function.
这看起来充满魔法，但不仅仅是魔法，Python对with的处理还很聪明。基本思想是with所求值的对象必须有一个__enter__()方法，一个__exit__()...
What is the common header format of Python files?
...d you will not have access to it in interactive sessions (i.e. through obj.__doc__) or when generating documentation with automated tools.
Import built-in modules first, followed by third-party modules, followed by any changes to the path and your own modules. Especially, additions to the path and n...
Among $_REQUEST, $_GET and $_POST which one is the fastest?
...
$_REQUEST, by default, contains the contents of $_GET, $_POST and $_COOKIE.
But it's only a default, which depends on variables_order ; and not sure you want to work with cookies.
If I had to choose, I would probably not us...
Extract traceback info from an exception object
...n you're using.
In Python 3
It's simple: exceptions come equipped with a __traceback__ attribute that contains the traceback. This attribute is also writable, and can be conveniently set using the with_traceback method of exceptions:
raise Exception("foo occurred").with_traceback(tracebackobj)
...
Why is __dirname not defined in node REPL?
From the node manual I see that I can get the directory of a file with __dirname , but from the REPL this seems to be undefined. Is this a misunderstanding on my side or where is the error?
...
What does $_ mean in PowerShell?
...ich is called $PSItem in Powershell 3 and newer.
1,2,3 | %{ write-host $_ }
or
1,2,3 | %{ write-host $PSItem }
For example in the above code the %{} block is called for every value in the array. The $_ or $PSItem variable will contain the current value.
...
How can I create a copy of an object in Python?
... get a copy method (in 2, you'd use a slice to make a copy):
>>> a_list = list('abc')
>>> a_copy_of_a_list = a_list.copy()
>>> a_copy_of_a_list is a_list
False
>>> a_copy_of_a_list == a_list
True
Shallow Copies
Shallow copies are just copies of the outermost cont...
std::function and std::bind: what are they, and when should they be used?
...ere are two left to go.
You can use std::bind to get g:
auto g = bind(f, _1, 4, _2);
This is more concise than actually writing a functor class to do it.
There are further examples in the article you link to. You generally use it when you need to pass a functor to some algorithm. You have a fun...
How to pretty-print a numpy.array without scientific notation and with given precision?
...
You can use set_printoptions to set the precision of the output:
import numpy as np
x=np.random.random(10)
print(x)
# [ 0.07837821 0.48002108 0.41274116 0.82993414 0.77610352 0.1023732
# 0.51303098 0.4617183 0.33487207 0.7116209...