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Replace None with NaN in pandas dataframe
...ata from an SQL database, you can combine this with the answer below. This converts None (which isn't a string) to NaN. Then you can df['column'].replace(nan, "", inplace=True) if say you wanted None to be empty string.
– VISQL
Jul 4 '18 at 12:52
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How do I remove the old history from a git repository?
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@Jez you can convert your shallow repo into normal one by running git filter-branch -- --all. This will change all hashes in it but after that you will be able to push it to a new repo
– Ed'ka
Jan 26...
Can I mix Swift with C++? Like the Objective-C .mm files
I just changed my .m files to .mm and use C++. Is there a way to do the same with Swift?
13 Answers
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Doctrine and composite unique keys
...ote that you have to provide column names, not field names. So you have to convert camelCase to snake_case and append _id for associations, because that's how Doctrine generates column names.
– gronostaj
Mar 6 '18 at 13:35
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When should I use C++ private inheritance?
...This is NOT a complete answer. Read other answers like here (conceptually) and here (both theoretic and practic) if you are interested in the question. This is just a fancy trick that can be achieved with private inheritance. While it is fancy it is not the answer to the question.
Besides the basic...
Does JSON syntax allow duplicate keys in an object?
...<a>x</a>
<a>y</a>
</object>
When this is converted into JSON, you get the following:
{
"object": {
"a": [
"x",
"y"
]
}
}
A natural mapping from a language that handles what you might call duplicate keys to another, can serve as a potential...
Java 8 NullPointerException in Collectors.toMap
...ws a NullPointerException if one of the values is 'null'. I don't understand this behaviour, maps can contain null pointers as value without any problems. Is there a good reason why values cannot be null for Collectors.toMap ?
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What is the difference between Θ(n) and O(n)?
...I see Θ(n) with the strange Θ symbol with something in the middle of it, and sometimes just O(n). Is it just laziness of typing because nobody knows how to type this symbol, or does it mean something different?
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How to find gaps in sequential numbering in mysql?
... far faster than the accepted answer. The only thing that I'd add is that CONVERT( YourCol, UNSIGNED ) will give better results if YourCol isn't already an integer.
– Barton Chittenden
Feb 10 '17 at 23:36
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Is optimisation level -O3 dangerous in g++?
...mpiling with an optimisation level of -O3 in g++ is somehow 'dangerous', and should be avoided in general unless proven to be necessary.
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