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django: BooleanField, how to set the default value to true?
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If you're just using a vanilla form (not a ModelForm), you can set a Field initial value ( https://docs.djangoproject.com/en/2.2/ref/forms/fields/#django.forms.Field.initial ) like
class MyForm(forms.Form):
my_field = fo...
Start may not be called on a promise-style task. exception is coming
...ask.Run or Task.Factory.StartNew to both create and start a new Task.
So, now we know to just get rid of that pesky Start. You'll run your code and find that the message box is shown right away, not 5 seconds later, what's up with that?
Well, Task.Delay just gives you a task that will be complete...
Include all existing fields and add new fields to document
...The $addFields stage is equivalent to a $project stage that explicitly specifies all existing fields in the input documents and adds the new fields.
db.collection.aggregate([
{ "$addFields": { "custom_field": "$obj.obj_field1" } }
])
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Reverse a string in Python
... It works by doing [begin:end:step] - by leaving begin and end off and specifying a step of -1, it reverses a string.
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C++实现一款简单完整的聊天室服务器+客户端 - C/C++ - 清泛网 - 专注C/C++及内核技术
...线程从缓冲区中取出消息
MessageBuffer.h
//MessageBuffer.h
#ifndef _MESSAGE_BUF_INCLUDE_
#define _MESSAGE_BUF_INCLUDE_
#include <pthread.h>
#define MESSAGE_COUNT 16
#define MESSAGE_LENGTH 2048
class MessageBuffer{
private:
pthread_mutex_t mutex;//访问缓冲的互斥量
pt...
About .bash_profile, .bashrc, and where should alias be written in? [duplicate]
...!), shell options with set and shopt, etc. For an example, see: My .bashrc
Now, as part of UNIX peculiarity, a login-shell does NOT execute ~/.bashrc but only ~/.profile or ~/.bash_profile, so you should source that one manually from the latter. You'll see me do that in my ~/.profile too: source ~/...
Is there a generator version of `string.split()` in Python?
...ra memory). This did not result in a noticeable growth of memory (that is, if there was a growth in memory, it was far far less than the 1GB string).
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What are the differences between Autotools, Cmake and Scons?
...ugh time in the rest of this month to sort the mess out...) for work right now as I'm typing this. Apache Thrift has one of those BROKEN build systems that won't cross-compile.)
The "normal" users are actually NOT going to just do "./configure; make"- for many things, they're going to be pulling a ...
MFC的多国语言界面的实现 - C/C++ - 清泛网 - 专注C/C++及内核技术
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SetThreadLocale(MAKELCID(MAKELANGID(LANG_CHINESE, SUBLANG_CHINESE_SIMPLIFIED), SORT_DEFAULT));
设置线程语言为“英语（美国）”的代码如下：
SetThreadLocale(MAKELCID(MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US), SORT_DEFAULT));
设置线程语言要在对话框创建之前...
How to convert R Markdown to PDF?
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Updated Answer (10 Feb 2013)
rmarkdown package:
There is now an rmarkdown package available on github that interfaces with Pandoc.
It includes a render function. The documentation makes it pretty clear how to convert rmarkdown to pdf among a range of other formats. This includes i...