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App Inventor 2 执行JavaScript代码教程 - WebView与JS交互 · App Inventor 2 中文网
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实战案例：用ECharts绘制图表
HTML文件（echarts_demo.html）
App Inventor积木块
实战案例：调用第三方JS库处理图像
HTML文件（image_processor.html）
数据传递注意事项
1. 转义特殊字符
2. ...
Calculate distance between 2 GPS coordinates
...y solution:
#include <math.h>
#include "haversine.h"
#define d2r (M_PI / 180.0)
//calculate haversine distance for linear distance
double haversine_km(double lat1, double long1, double lat2, double long2)
{
double dlong = (long2 - long1) * d2r;
double dlat = (lat2 - lat1) * d2r;
...
Regular Expression for alphanumeric and underscores
...that contains only those characters (or an empty string), try
"^[a-zA-Z0-9_]*$"
This works for .NET regular expressions, and probably a lot of other languages as well.
Breaking it down:
^ : start of string
[ : beginning of character group
a-z : any lowercase letter
A-Z : any uppercase letter
0-...
What is the difference between '/' and '//' when used for division?
...he 2.x line, there is no difference for integers unless you perform a from __future__ import division, which causes Python 2.x to adopt the 3.x behavior.
Regardless of the future import, 5.0 // 2 will return 2.0 since that's the floor division result of the operation.
You can find a detailed descr...
Getting a list of all subdirectories in the current directory
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Do not use os.walk('.').next()[1] or os.walk('.').__next__()[1] directly. Instead, use the built-in function next(), which is available both in Python 2 (see doc) and Python 3 (see doc). For example: next(os.walk('.'))[1].
– Lucio Paiva
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SPAN vs DIV (inline-block)
...gt;
<style>
/* Nur für das w3school Bild */
#w3_DIV_1 {
bottom: 0px;
box-sizing: border-box;
height: 391px;
left: 0px;
position: relative;
right: 0px;
text-size-adjust: 100%;
t...
How do you test that a Python function throws an exception?
...t ahold of the actual Exception object thrown:
import unittest
def broken_function():
raise Exception('This is broken')
class MyTestCase(unittest.TestCase):
def test(self):
with self.assertRaises(Exception) as context:
broken_function()
self.assertTrue('This i...
Windows下如何判断Win32 or x64？ - C/C++ - 清泛网 - 专注C/C++及内核技术
...判断Win32 or x64？MSDN 里说，VC 有 3 个预处理常量，分别是 _WIN32，_WIN64，WIN32。这三个常量如何使用呢？看起来简单，其实是很困惑的。 在 Win3...MSDN 里说，VC 有 3 个预处理常量，分别是 _WIN32，_WIN64，WIN32。这三个常量如何使用...
error LNK2019: 无法解析的外部符号_socket，该符号在函数 中被引用 - c++1...
1>NetClient.obj : error LNK2019: 无法解析的外部符号 _closesocket@4，该符号在函数 _main 中被引用
1>NetClient.obj : error LNK2019: 无法解析的外部符号 _inet_ntoa@4，该符号在函数 _main 中被引用
1>NetClient.obj : error LNK2019: 无法解析的外部符...
Best way to replace multiple characters in a string?
...ompile('([&#])')
def d(text):
text = RX.sub(r'\\\1', text)
def mk_esc(esc_chars):
return lambda s: ''.join(['\\' + c if c in esc_chars else c for c in s])
esc = mk_esc('&#')
def e(text):
esc(text)
def f(text):
text = text.replace('&', '\&').replace('#', '\#')
de...