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App Inventor 2 扩展开发实战：从Java小白到发布第一个.aix自定义插件 - Ap...
App Inventor 2 扩展开发实战：从Java小白到发布第一个.aix自定义插件
刚接触App Inventor 2时，大部分人会被它现成的组件库"惯坏"——想听歌有Player、想拍照有Camera、想存数据有TinyDB。但做着做着就发现，有些需求官方组件...
Replacing Pandas or Numpy Nan with a None to use with MysqlDB
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203
@bogatron has it right, you can use where, it's worth noting that you can do this natively in ...
How can I read inputs as numbers?
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321
TLDR
Python 3 doesn't evaluate the data received with input function, but Python 2's input fu...
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb
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22 Answers
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Retrieving Android API version programmatically
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edited Jan 28 '17 at 19:30
Siarhei
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Explain the encapsulated anonymous function syntax
...ve a function expression without a name defined:
(function () {
alert(2 + 2);
}());
Or named function expression:
(function foo() {
alert(2 + 2);
}());
The Parentheses (formally called the Grouping Operator) can surround only expressions, and a function expression is evaluated.
The tw...
How to replace a hash key with another key
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720
hash[:new_key] = hash.delete :old_key
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How does PHP 'foreach' actually work?
...function iterate($arr) {
foreach ($arr as $v) {}
}
$outerArr = [0, 1, 2, 3, 4];
iterate($outerArr);
Here, $arr will be duplicated to prevent IAP changes on $arr from leaking to $outerArr. In terms of the conditions above, the array is not a reference (is_ref=0) and is used in two places (refc...
Turning multi-line string into single comma-separated
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You can use awk and sed:
awk -vORS=, '{ print $2 }' file.txt | sed 's/,$/\n/'
Or if you want to use a pipe:
echo "data" | awk -vORS=, '{ print $2 }' | sed 's/,$/\n/'
To break it down:
awk is great at handling data broken down into fields
-vORS=, sets the "output re...
MySQL Great Circle Distance (Haversine formula)
...& Google Maps:
Here's the SQL statement that will find the closest 20 locations that are within a radius of 25 miles to the 37, -122 coordinate. It calculates the distance based on the latitude/longitude of that row and the target latitude/longitude, and then asks for only rows where the dis...