To make my code more elegant, I need to wrap a context manager with initialization code as a function in Python. This is definitely possible, but it took me some time to find the most elegant way to do this.
Generally speaking, you will want to enter all contexts when using the decorator
@contextlib.asynccontextmanager. When the end user uses
with my_function() as a:, everything inside the
with block has been inside the nested contexts. When Python gets out of the end user's
with block, it should also run all related
__exit__s in the wrapper function. See example (requires Python 3.7+ probably and writes
test.txt; you can test it on repl.it):
async def my_context_manager() -> typing.ContextManager[aiofiles.threadpool.AsyncFileIO]:
filename = 'test.txt'
async with aiofiles.open(filename, 'w+') as file:
# you can still override or interact with `file` if needed
async def main():
# end user
async with my_context_manager() as myfile:
When I rewrite the code above I feel it so easy and natural. It really took me some time to realize how this works.
Spending 2 hours on this because 1) I don't have experience with Gradle script (its syntax looks funky) 2) DJI sxxks, and they put 50MB of large assets files to their SDK, which is camera distrotion_correction files that I never need, and 3) Android Gradle library upgrades, which deprecating mergeAssets.
Looking at some GitHub projects's Gradle script, it looks like
dependsOn is very popular in defining what order the task should be executed, and it works! 继续阅读“Strip Assets Files in new Android Gradle”
WordPress 版本都到 4.9 了，全球 CMS 占有量也早过三分之一了，自动更新居然还是全量下载，连个增量更新都不做（光做 no-content.zip 有啥用拜托？）。虚拟主机下载 WordPress 的包速度又很慢，结果总是超时（虚拟主机控制的那种超时断开），更新失败。
My WordPress auto update always failed because of slow download speed. Just don't know why WordPress doesn't implement a incremental upgrade mechanism (maybe I should search for a ticket?). Whatever, I have to solve it manually, in a smart way.
P.S. 写完这篇之后，看到更新的 API 了，的确是有增量更新的，但他们不用。They actually have incremental upgrade implemented, but they hardly use it.
继续阅读“Manual work after WordPress auto update failed”
- 网站 Website (包含导出数据查看网页 Includes a webpage for reading the exported file)
- 演示 Demo (这是扩展的欢迎界面，显示效果与实际扩展工作情况无异 This is the introduction page of the extension, which reuses the same core scripts of the parsing code, working identically to the extension)
- Chrome Web Store
由于原网站在今年改版，成绩查询服务器已经下线，该扩展的读取成绩功能已经无法工作。但因为扩展自定义了一套 JSON 数据结构，即便服务器不可用，仍可通过离线数据实现信息显示，因此在线演示、导出成绩查看器等仍可查看。
Due to the original website upgrade, this Chrome extension cannot fetch grade data any more (the grade check server is down). However, the demo and the exported data reader still work, because I have implemented a customized JSON data structure, which make the code functional by reading the JSON data even if the remote server is unavailable. 继续阅读“jzGradeChecker - 优雅查成绩 Graceful Grade-Checking Experience”
This is a course project for "Scientific Research Project Guidance and Training" course of my major. We chose to build a Rubik's cube solving robot, which can identify a third-order cube's pattern and solve it.
该机器人拥有六个自由度，对六个面进行旋转，并有四个摄像头从四个角进行颜色的识别。此外，机器人采用树莓派作为上位机进行总体控制，采用 Arduino 作为下位机进行步进电机的控制。
The robot has six degrees of freedom, rotating the six sides. It identifies the cube by four cameras from the four corners. A Raspberry Pi is used as an upper controller for the general control, and an Arduino board as a lower controller for the motor control.
项目在最终结题答辩时获得非常高的评价，同一课程中共有 9 组项目。之后，项目在 2017 年全国青年科普创作实验暨作品大赛中获得北京赛区未来教育组三等奖。
The project gets an excellent feedback at the final presentation among 9 projects of the course. Afterwards we also won a third prize (Beijing Area/FutureEDU) in 2017 China Youth Science Popularization Experiment and Work Contest.
继续阅读“魔方机器人（网页与 Python 控制程序） Rubik's Cube Solving Robot”
This article is an English one, because I really need to work on the language. Sorry if it is not easy to understand.
A Summary to What's Happening Recently
Recently in my campus, IT service is very unstable.
- In March, many people posted on forums that they tried to top up campus Internet account by WeChat, but more money (maybe 100x) than they paid were topped up.
- Later WeChat top-up service were disabled. Because most people were not aware of the existing offline top-up-by-card service, many of them became arrearage.
- Several days later, campus Internet's charging system was disabled, which means you can use it for free. Later the charging system was resumed, but only charging at the monthly fee (not counting flux fee).
- An unnoticeable statement was published then, indicating that it was caused by a bug from the software company.
- On March 20th, campus card users who used their cards to drink hot water or eat breakfast, found their card locked. (Those lazy guys were not affected at all)
- In the morning nobody knows whether the issue was being solved, until at around 11 (lunchtime) my school's instructor sent an announcement that
"there will be unlock service in canteens, please keep order and don't panic at the scene". At canteens announcements by canteens' administrator is put up. Unlocking was quick and easy, but most people still went to canteens where Alipay is accepted.
- Later that afternoon public statement by card administrator was out: It was a service fault (on BITUnion some said that it's a bug hidden for 14 years). IT staffs explained on BITUnion that they tried to work out solutions and mitigate the issue before they drafted public statements.
- In these months campus Internet is unstable: During peak hours it became very slow or even unavailable. Maybe it's around 2%'s downtime (in a 24-hour aspect), looking not that much, but users surely could experience that.
- The causes seem very complex. In my view, new DNS servers, old cache servers, new firewall systems, new upstream link providers and upstream link issue all can cause problems. And of course those new facilities all need to be fine-tuned, which takes time.
- Currently no authentic statement is published. But in the IT service monthly report (which most people are not aware of), it said "Issue fully fixed, during peak hours upstream links can work in full bandwidth now". One of the reasons they mentioned was "DDoS attack causing network core server CPU instant usage up to 99% (usually ~20%)".
- However, as student representatives meeting will be held, many representatives will raise the heated Internet issue onto the meeting. But I believe most of they will never get the point why this is happening.
继续阅读“Make Service Fault Transparent”
学院每学期会对学生进行“综合测评”。测评规则最早较为简单，可以通过网上常用的电子表单服务实现，但随着测评规则和配套表格的复杂化，其他班级不得不回到填写 Word 表格后手工统计的模式。本系统集成了测评表格和计算规则，设计用于班级内的测评表格收集、自动统计，直接导出要求的测评结果表格，并支持多班级分别使用。
系统在班内（29 人）已使用两个学期，应实际使用需求，在使用过程中增加了测评项目、单次填写多学期的支持。此外系统也为其他 1 个班级提供过服务。使用过的班长均反馈效果良好。 继续阅读“学院综合测评系统 Student Evaluation System”
- 开源的 PHP 教务系统读取库，以对象形式调用并处理正方教务系统中的课表、校历、成绩等信息，且可自动利用调课信息对课表进行修改；
- 调用上述接口，将教务信息保存至系统内，并导出为 JSON 文件的 PHP 采集模块；
- 读取导出的 JSON 文件，在浏览器内离线对教务信息进行分析显示的分析模块。
借助读取库和一小点代码，可将课表生成为 iCalendar 文件，导入进日历软件。 继续阅读“bPlanner 多学生教务信息整合系统”
汕头市位于广东省，是中国第一批 4 个经济特区之一。目前其市区内的实时公交信息只通过一款手机应用发放，其对于日常使用而言，体验仍过于复杂，乘客需要打开应用 > 手动输入线路或点击“当前站点”按钮后、选择当前站点和线路 > 查看线路情况。
在参考了 Citymapper、Transit 等应用的设计后，给出了一个基于网页的实时公交查询设计。在同一个页面上，由上至下列出当前位置附近所有方向线路的来车状态，并以站点分组，点击线路后会显示路线图和车辆情况，大大优化了日常查询实时公交的体验。
网页显示的实时公交数据，需要借助后端 PHP 程序抓取。程序设置了缓存机制，此外还通过保存每辆车的历史位置，对长时间不移动的车辆进行标注提示，提升了数据的可信度。 继续阅读“汕头实时公交网页设计 Realtime Bus in Shantou”