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mongodb group values by multiple fields
...tems to $push to an array.
db.books.aggregate([
{ "$group": {
"_id": {
"addr": "$addr",
"book": "$book"
},
"bookCount": { "$sum": 1 }
}},
{ "$group": {
"_id": "$_id.addr",
"books": {
"$push": {
...
Understanding the main method of python [duplicate]
...is almost unique to the language(*).
The semantics are a bit subtle. The __name__ identifier is bound to the name of any module as it's being imported. However, when a file is being executed then __name__ is set to "__main__" (the literal string: __main__).
This is almost always used to separate...
How to make a cross-module variable?
The __debug__ variable is handy in part because it affects every module. If I want to create another variable that works the same way, how would I do it?
...
How to implement a binary tree?
...plementation of binary search tree.
#!/usr/bin/python
class Node:
def __init__(self, val):
self.l = None
self.r = None
self.v = val
class Tree:
def __init__(self):
self.root = None
def getRoot(self):
return self.root
def add(self, val):
...
Django filter queryset __in for *every* item in list
...oManyField('Tag')
class Tag(models.Model):
name = models.CharField(max_length=50)
def __unicode__(self):
return self.name
In [2]: t1 = Tag.objects.create(name='holiday')
In [3]: t2 = Tag.objects.create(name='summer')
In [4]: p = Photo.objects.create()
In [5]: p.tags.add(t1)
In [6]...
What is a None value?
... this book?because his name is Jason R. Briggs.
– The_Diver
Oct 20 '13 at 18:52
...
What do commas and spaces in multiple classes mean in CSS?
...
.container_12 .grid_6,
.container_16 .grid_8 {
width: 460px;
}
That says "make all .grid_6's within .container_12's and all .grid_8's within .container_16's 460 pixels wide." So both of the following will render the same:
<di...
Safe characters for friendly url [closed]
...igits, hyphen, period, underscore, and tilde."
ALPHA DIGIT "-" / "." / "_" / "~"
Note that RFC 3986 lists fewer reserved punctuation marks than the older RFC 2396.
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...
How to get instance variables in Python?
...
Every object has a __dict__ variable containing all the variables and its values in it.
Try this
>>> hi_obj = hi()
>>> hi_obj.__dict__.keys()
share...
Determining 32 vs 64 bit in C++
...vironment or not and use that to set my variables.
// Check windows
#if _WIN32 || _WIN64
#if _WIN64
#define ENVIRONMENT64
#else
#define ENVIRONMENT32
#endif
#endif
// Check GCC
#if __GNUC__
#if __x86_64__ || __ppc64__
#define ENVIRONMENT64
#else
#define ENVIRONMENT32
#endif
#endif
Another easi...