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An item with the same key has already been added
...this error whenever I submit the form also the action method is not being called because of this:
21 Answers
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Convert Pandas column containing NaNs to dtype `int`
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@jsc123 you can use the object dtype. This comes with a small health warning but for the most part works well.
– Andy Hayden
May 19 '15 at 15:16
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What does !! mean in ruby?
...:
!!nil #=> false
!!"abc" #=> true
!!false #=> false
It's usually not necessary to use though since the only false values to Ruby are nil and false, so it's usually best to let that convention stand.
Think of it as
!(!some_val)
One thing that is it used for legitimately is preventi...
What's the difference between & and && in MATLAB?
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@neuronet it isn't really about efficiency, more that it permits a construct where the first expression guarantees a condition without which the second expression may cause a run-time error. e.g. d != 0 && 1/d vs d !=0 & 1/d - the ...
Can an int be null in Java?
... @BrianAgnew Let me rectify what I said here, I was plain wrong, I basically didn't realize that int i = (Integer)null; will throw NPE at run-time while unboxing it.
– sactiw
Jan 23 '16 at 12:22
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How to take backup of a single table in a MySQL database?
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SQL usually compresses well--you can pipe the command above through gzip and the resulting file will be much smaller: mysqldump db_name table_name | gzip > table_name.sql.gz to restore: gunzip < table_name.sql.gz | mysql -u...
How do I loop through a list by twos? [duplicate]
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@RoelVandePaar, No that is still an integer. Actually I found the answer. import numpy as np for i in np.arange(-3.14, 3.14, 0.1): print (i)
– Kevin Patel
May 20 at 17:40
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With Spring can I make an optional path variable?
...ve optional path variables, but you can have two controller methods which call the same service code:
@RequestMapping(value = "/json/{type}", method = RequestMethod.GET)
public @ResponseBody TestBean typedTestBean(
HttpServletRequest req,
@PathVariable String type,
@RequestP...
Why does a base64 encoded string have an = sign at the end
...org/wiki/Base64#Output_padding is pretty good. But the answer by Badr is really a better one (it just hasn't caught up in votes yet).
– NH.
Jul 9 '19 at 18:58
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Xcode iOS project only shows “My Mac 64-bit” but not simulator or device
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This is basically happen, when you change your project name or something like that. The solution is, you have to select the right "Scheme" for your project. Here is the solution :
After open your project :
Go to "Product" from upper m...