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MongoDB数据导出导入工具：mongoexport,mongoimport - 大数据 & AI - 清泛...
...个students集合，集合中数据如下：
> db.students.find()
{ "_id" : ObjectId("5031143350f2481577ea81e5"), "classid" : 1, "age" : 20, "name" : "kobe" }
{ "_id" : ObjectId("5031144a50f2481577ea81e6"), "classid" : 1, "age" : 23, "name" : "nash" }
{ "_id" : ObjectId("5031145a50f2481577ea81...
how to get the current working directory's absolute path from irb
...ssible from irb? Apparently from a script it's possible using File.expand_path(__FILE__)
6 Answers
...
Get class that defined method
...
import inspect
def get_class_that_defined_method(meth):
for cls in inspect.getmro(meth.im_class):
if meth.__name__ in cls.__dict__:
return cls
return None
...
Elegant Python function to convert CamelCase to snake_case?
...se
import re
name = 'CamelCaseName'
name = re.sub(r'(?<!^)(?=[A-Z])', '_', name).lower()
print(name) # camel_case_name
If you do this many times and the above is slow, compile the regex beforehand:
pattern = re.compile(r'(?<!^)(?=[A-Z])')
name = pattern.sub('_', name).lower()
To handle mor...
What is __gxx_personality_v0 for?
... quick grep of the libstd++ code base revealed the following two usages of __gx_personality_v0:
In libsupc++/unwind-cxx.h
// GNU C++ personality routine, Version 0.
extern "C" _Unwind_Reason_Code __gxx_personality_v0
(int, _Unwind_Action, _Unwind_Exceptio...
Circle line-segment collision detection algorithm?
...dy - dxh - dyk ) +
ex2 + ey2 -
2exh - 2eyk + h2 + k2 - r2 = 0
Finally,
t2( _d * _d ) + 2t( _e * _d - _d * _c ) + _e * _e - 2( _e*_c ) + _c * _c - r2 = 0
*Where _d is the vector d and * is the dot product.*
And then,
t2( _d * _d ) + 2t( _d * ( _e - _c ) ) + ( _e - _c ) * ( _e - _c ) - r2 = 0
Letting...
Why does ReSharper tell me “implicitly captured closure”?
...r generates a type looks like :
[CompilerGenerated]
private sealed class c__DisplayClass2
{
public object x;
public ValueStore store;
public c__DisplayClass2()
{
base.ctor();
}
//Represents the first lambda expression: () => store.SetValue(x)
public void Capturedb__0()
{
...
Python integer division yields float
... -, * and / to special functions, such that e.g. a + b is equivalent to
a.__add__(b)
Regarding division in Python 2, there is by default only / which maps to __div__ and the result is dependent on the input types (e.g. int, float).
Python 2.2 introduced the __future__ feature division, which cha...
What does = +_ mean in JavaScript
I was wondering what the = +_ operator means in JavaScript. It looks like it does assignments.
12 Answers
...
What's the difference between a Python “property” and “attribute”?
...ggs)
it looks up eggs in spam, and then examines eggs to see if it has a __get__, __set__, or __delete__ method — if it does, it's a property. If it is a property, instead of just returning the eggs object (as it would for any other attribute) it will call the __get__ method (since we were ...