大约有 45,000 项符合查询结果（耗时：0.0463秒） [XML]
Why is `[` better than `subset`?
...(subset(x, condition))
}
subscramble(mtcars, cyl == 4)
This returns the error:
Error in eval(expr, envir, enclos) : object 'cyl' not found
because R no longer "knows" where to find the object called 'cyl'. He also points out the truly bizarre stuff that can happen if by chance there is an o...
Does SQLAlchemy have an equivalent of Django's get_or_create?
... Look at Django's implementation of get_or_create. It checks for integrity error, and relies upon proper use of unique constraints.
– Ivan Virabyan
May 21 '12 at 6:17
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Is there any way I can define a variable in LaTeX?
...xisting macros without any warnings and therefore can cause various subtle errors. To overcome this either use namespaced variables like my_var or fall back to \newcommand, \renewcommand commands instead.
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Heroku Postgres - terminate hung query (idle in transaction)
...sion of postgres are you using? (hint: select version()). Do you get any error messages when using pg_cancel_backend?
– tobixen
Jul 2 '12 at 12:21
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Logical operator in a handlebars.js {{#if}} conditional
...s that you have to pass the operator as a string or else the compiler will error out while tokenizing your template. {{#ifCond true '==' false}}
– Joe Holloway
Jul 11 '13 at 20:11
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'python' is not recognized as an internal or external command [duplicate]
...t the problem is, when I go to cmd and type python testloop.py I get the error:
15 Answers
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If isset $_POST
...to avoid the ! operator in cases like this (easier to read, less chance of error, etc.) and reverse the logic... if (empty()) {/* No */} else {/* Yes */}
– MrWhite
Aug 1 '14 at 10:58
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R: Comment out block of code [duplicate]
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Richie, nice suggestion, but slashes will generate error messages:Error: unexpected '/' in: "#( # start of comment http:/"
– PatrickT
Mar 11 '13 at 14:32
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Convert integer into its character equivalent, where 0 => a, 1 => b, etc
... And when you have no need of extending, maybe more prone to errors? abcede
– Nelson Rothermel
Jun 29 '10 at 22:07
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DropDownList's SelectedIndexChanged event not firing
...e was invalid but because I use the Telerik RadAjaxManager on my pages the error was not showing when I tested in my browser. When I commented out the entire RadAjaxManager the error presented itself and I was able to fix it.
– user2721607
Jul 26 '17 at 11:46
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