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App Inventor 2 EV3超声波传感器教程 · App Inventor 2 中文网
...通过蓝牙连接EV3，读取各种传感器。
已有文档：bluetooth_remote.md 介绍了蓝牙通信。本文聚焦EV3超声波传感器。
EV3组件
添加组件
组件面板 → LEGO MINDSTORMS → **Ev3 Ultrasonic Sensor`
支持的...
Why doesn't list have safe “get” method like dictionary?
...f your list).
Of course, you can easily implement this yourself:
def safe_list_get (l, idx, default):
try:
return l[idx]
except IndexError:
return default
You could even monkeypatch it onto the __builtins__.list constructor in __main__, but that would be a less pervasive change since...
In Python, if I return inside a “with” block, will the file still close?
...
@RikPoggi os._exit is sometimes used - it exits the Python process without calling cleanup handlers.
– Acumenus
Oct 8 '16 at 6:25
...
How to manually create icns files using iconutil?
...
The following files should exist: icon_16x16.png, icon_16x16@2x.png, icon_32x32.png, icon_32x32@2x.png, icon_128x128.png, icon_128x128@2x.png, icon_256x256.png, icon_256x256@2x.png. The @2x files should be stored at 144 pixels per inch while the others should be...
'printf' vs. 'cout' in C++
...in practice with printf is const char * (C string, can be obtained using to_c method of std::string)). For instance, to print size_t, you need to use %zd, while int64_t will require using %"PRId64". The tables are available at http://en.cppreference.com/w/cpp/io/c/fprintf and http://en.cppreference....
How to serve static files in Flask
...entation Flask describes returning static files. Yes, I could use render_template but I know the data is not templatized. I'd have thought send_file or url_for was the right thing, but I could not get those to work. In the meantime, I am opening the files, reading content, and rigging up a ...
Django select only rows with duplicate field values
...values('name')
.annotate(Count('id'))
.order_by()
.filter(id__count__gt=1)
This is as close as you can get with Django. The problem is that this will return a ValuesQuerySet with only name and count. However, you can then use this to construct a regula...
关于php的socket初探 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...塞的古老模型：属于同步阻塞 IO 模型，代码如下：
socket_server.php
<?php
/**
* SocketServer Class
* By James.Huang <shagoo#gmail.com>
**/
set_time_limit(0);
class SocketServer
{
private static $socket;
function SocketServer($port)
{ ...
Assignment inside lambda expression in Python
...asons. For example, we will be able to write the following:
import sys
say_hello = lambda: (
message := "Hello world",
sys.stdout.write(message + "\n")
)[-1]
say_hello()
In Python 2, it was possible to perform local assignments as a side effect of list comprehensions.
import sys
say_hell...
How do I get a Cron like scheduler in Python? [closed]
...do(job)
schedule.every().day.at("10:30").do(job)
while 1:
schedule.run_pending()
time.sleep(1)
Disclosure: I'm the author of that library.
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