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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": {
...
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...
efficient circular buffer?
...1] #[10, 11, 3, 8] 3, 11
Class:
class circularlist(object):
def __init__(self, size, data = []):
"""Initialization"""
self.index = 0
self.size = size
self._data = list(data)[-size:]
def append(self, value):
"""Append an element"""
if le...
How to add a 'or' condition in #ifdef
...¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯|//
#ifdef CONDITION_01 //| |//
#define TEMP_MACRO //| |//
#endif //| |//
#ifdef CONDITION_02 //| |//
#define TEMP_MACRO //| |//
#endif ...
Or versus OrElse
...([0] object a,
[1] int32 b,
[2] bool CS$4$0000)
IL_0000: nop
IL_0001: ldnull
IL_0002: stloc.0
IL_0003: ldc.i4.3
IL_0004: stloc.1
IL_0005: ldloc.0
IL_0006: ldnull
IL_0007: ceq
IL_0009: ldloc.0
IL_000a: callvirt instance string [mscorlib]...
How do you generate dynamic (parameterized) unit tests in python?
...,
["bar", "a", "b"],
["lee", "b", "b"],
])
def test_sequence(self, name, a, b):
self.assertEqual(a,b)
Which will generate the tests:
test_sequence_0_foo (__main__.TestSequence) ... ok
test_sequence_1_bar (__main__.TestSequence) ... FAIL
test_sequence_2_lee (__main_...
Why prefer two's complement over sign-and-magnitude for signed numbers?
...icle on two's complement for the full answer: en.wikipedia.org/wiki/Two%27s_complement. The short answer is the MSB 1 indicates -8, and the remaining three 1s indicate 4, 2, and 1, respectively, so -8+4+2+1 = -1.
– Welbog
Aug 23 '16 at 13:33
...
Python: Bind an Unbound Method?
...
All functions are also descriptors, so you can bind them by calling their __get__ method:
bound_handler = handler.__get__(self, MyWidget)
Here's R. Hettinger's excellent guide to descriptors.
As a self-contained example pulled from Keith's comment:
def bind(instance, func, as_name=None):
...
vs2008编译boost详细步骤 - 开源 & Github - 清泛网 - 专注C/C++及内核技术
...映射到Python之中；
（9）Pool，内存池管理；
（10）smart_ptr，智能指针。
【二、Boost库的编译】
【Setp1 准备工作】：
（1）Boost 下载可以到官方网站下载：
http://www.boost.org/
（2）安装VS2008 IDE
【Setp2 编译Boost】
1.打开Vi...
Python __str__ and lists
...
Calling string on a python list calls the __repr__ method on each element inside. For some items, __str__ and __repr__ are the same. If you want that behavior, do:
def __str__(self):
...
def __repr__(self):
return self.__str__()
...