大约有 43,000 项符合查询结果（耗时：0.0490秒） [XML]
Approximate cost to access various caches and main memory?
Can anyone give me the approximate time (in nanoseconds) to access L1, L2 and L3 caches, as well as main memory on Intel i7 processors?
...
Difference between a theta join, equijoin and natural join
I'm having trouble understanding relational algebra when it comes to theta joins, equijoins and natural joins. Could someone please help me better understand it? If I use the = sign on a theta join is it exactly the same as just using a natural join?
...
Serializing class instance to JSON
I am trying to create a JSON string representation of a class instance and having difficulty. Let's say the class is built like this:
...
Accessing dict keys like an attribute?
... Unless - of course - you assign some value to them, see below)
Attributes and items are always in sync
Trying to access non-existent key as an attribute correctly raises AttributeError instead of KeyError
Supports [Tab] autocompletion (e.g. in jupyter & ipython)
Cons:
Methods like .keys() wil...
What is the purpose of the -m switch?
...line of the Rationale section of PEP 338 says:
Python 2.4 adds the command line switch -m to allow modules to be located using the Python module namespace for execution as scripts. The motivating examples were standard library modules such as pdb and profile, and the Python 2.4 implementation is...
vs2008编译boost详细步骤 - 开源 & Github - 清泛网 - 专注C/C++及内核技术
...工程， 配置工程属性
设置包含文件目录F:\Develop\BoostlibAndDll\include\boost-1_37\boost
设置引用文件目录:F:\Develop\BoostlibAndDll\lib
完成后，可以使用。
【三、介绍Bjam使用】
Usage:
Bjam [options] [properties] [install|stage]
instal...
unique object identifier in javascript
I need to do some experiment and I need to know some kind of unique identifier for objects in javascript, so I can see if they are the same. I don't want to use equality operators, I need something like the id() function in python.
...
How can I dynamically create derived classes from a base class
...
This bit of code allows you to create new classes with dynamic
names and parameter names.
The parameter verification in __init__ just does not allow
unknown parameters, if you need other verifications, like
type, or that they are mandatory, just add the logic
there:
class BaseClass(object):...
Split data frame string column into multiple columns
... stringr::str_split_fixed
library(stringr)
str_split_fixed(before$type, "_and_", 2)
share
|
improve this answer
|
follow
|
...
Differences between lodash and underscore [closed]
...nsistent cross-environment iteration support for arrays, strings, objects, and arguments objects1. It has since become a superset of Underscore, providing more consistent API behavior, more features (like AMD support, deep clone, and deep merge), more thorough documentation and unit tests (tests whi...