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How to reshape data from long to wide format
...
And, as of data.table v1.9.6 we can cast on multiple columns
## add an extra column
dat1[, value2 := value * 2]
## cast multiple value columns
dcast(dat1, name ~ numbers, value.var = c("value", "value2"))
# name value_1 value_2 value_3 value_4 value2_1 value2_2 value2_3 ...
Django rest framework nested self-referential objects
... For anyone new viewing this question, I found that for each extra recursive level, I had to a repeat of the last line in the second edit. Strange workaround, but seems to work.
– Jeremy Blalock
Apr 11 '13 at 0:55
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How to insert a newline in front of a pattern?
...Linux and OS X:
sed 's/regexp/\'$'\n/g'
In general, for $ followed by a string literal in single quotes bash performs C-style backslash substitution, e.g. $'\t' is translated to a literal tab. Plus, sed wants your newline literal to be escaped with a backslash, hence the \ before $. And finally, ...
Remove ActiveRecord in Rails 3
...evious comment... in Rails 3.1, it is now --skip-active-record. Notice the extra dash.
– Mark Embling
Sep 3 '11 at 13:56
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Removing “NUL” characters
I have got characters like that in my notepad++
7 Answers
7
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How to define @Value as optional
...r example was @Value("${myValue:DEFAULT}").
You are not limited to plain strings as default values. You can use SPEL expressions, and a simple SPEL expression to return null is:
@Value("${myValue:#{null}}")
share
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Are there any side effects of returning from inside a using() statement?
... be called too.
While you certainly could take the longer route, it's two extra lines that just add cruft and extra context to keep track of (mentally). In fact, you don't really need the extra local variable - although it can be handy in terms of debugging. You could just have:
public static Tran...
How do I access the request object or any other variable in a form's clean() method?
...y.
A much better way is to override the form's __init__ method to take an extra keyword argument, request. This stores the request in the form, where it's required, and from where you can access it in your clean method.
class MyForm(forms.Form):
def __init__(self, *args, **kwargs):
se...
GCC -g vs -g3 GDB Flag: What is the Difference?
...ging information. On most systems that use stabs format, -g
enables use of extra debugging information that only GDB can use; this
extra information makes debugging work better in GDB but probably
makes other debuggers crash or refuse to read the program. If you want
to control for certain whether t...
Converting numpy dtypes to native python types
...pn.item()
print('{0} ({1!r}) -> {2}'.format(name, npn.dtype.char, type(nat)))
except:
pass
There are a few NumPy types that have no native Python equivalent on some systems, including: clongdouble, clongfloat, complex192, complex256, float128, longcomplex, longdo...