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How do I perform the SQL Join equivalent in MongoDB?
...rect. The new $lookup operator added to the aggregation pipeline is essentially identical to a left outer join:
https://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <...
Python - Get path of root project structure
...to prevent directories with a common name, such as string, from unintentionally hiding valid modules that occur later on the module search path. In the simplest case, __init__.py can just be an empty file, but it can also execute initialization code for the package or set the __all__ variable, descr...
Determining 32 vs 64 bit in C++
...esentation. I prefer ENVIRONMENT64 / ENVIRONMENT32. Then I find out what all of the major compilers use for determining if it's a 64 bit environment or not and use that to set my variables.
// Check windows
#if _WIN32 || _WIN64
#if _WIN64
#define ENVIRONMENT64
#else
#define ENVIRONMENT32
#endif...
Why does this loop produce “warning: iteration 3u invokes undefined behavior” and output more than 4
...
If during the evaluation of an expression, the result is not mathematically defined or not in the range of
representable values for its type, the behavior is undefined. [ Note: most existing implementations of C++
ignore integer overflows. Treatment of division by zero, forming a remainde...
How do exceptions work (behind the scenes) in c++
...
Instead of guessing, I decided to actually look at the generated code with a small piece of C++ code and a somewhat old Linux install.
class MyException
{
public:
MyException() { }
~MyException() { }
};
void my_throwing_function(bool throwit)
{
if (...
Get exception description and stack trace which caused an exception, all as a string
...
See the traceback module, specifically the format_exc() function. Here.
import traceback
try:
raise ValueError
except ValueError:
tb = traceback.format_exc()
else:
tb = "No error"
finally:
print tb
...
“Private” (implementation) class in Python
I am coding a small Python module composed of two parts:
7 Answers
7
...
Where should signal handlers live in a django project?
...
I actually like to make them classmethods of the model itself. That keeps everything within one class, and means you don't have to worry about importing anything.
...
A simple explanation of Naive Bayes Classification
... & part two being the confusion surrounding Training set.
In general all of Machine Learning Algorithms need to be trained for supervised learning tasks like classification, prediction etc. or for unsupervised learning tasks like clustering.
During the training step, the algorithms are taught...
Standard way to embed version into python package?
...is also used in lots of 3rd-party modules, so it's the quasi-standard.
Usually, __version__ is a string, but sometimes it's also a float or tuple.
Edit: as mentioned by S.Lott (Thank you!), PEP 8 says it explicitly:
Module Level Dunder Names
Module level "dunders" (i.e. names with two lea...