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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...
Remove an item from a dictionary when its key is unknown
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92
Be aware that you're currently testing for object identity (is only returns True if both operand...
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb
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22 Answers
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Active
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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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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...
SQL WHERE condition is not equal to?
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You can do like this
DELETE FROM table WHERE id NOT IN ( 2 )
OR
DELETE FROM table WHERE id <> 2
As @Frank Schmitt noted, you might want to be careful about the NULL values too. If you want to delete everything which is not 2(including the NULLs) then add OR id IS NULL...