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How to implement an STL-style iterator and avoid common pitfalls?
...requirements for an iterator to be "STL-style" and what are some other pitfalls to avoid (if any)?
8 Answers
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Error :Request header field Content-Type is not allowed by Access-Control-Allow-Headers
... extra header. Try prepending the following to your file if you are using PHP:
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept");
Make sure that you haven't already used header in another file, or you will get a nasty...
What __init__ and self do on Python?
...to declare it explicitly. When you create an instance of the A class and call its methods, it will be passed automatically, as in ...
a = A() # We do not pass any argument to the __init__ method
a.method_a('Sailor!') # We only pass a single argument
The __init__ method is roughly w...
What does the restrict keyword mean in C++?
...
A restrict-qualified pointer (or reference)...
! ...is basically a
promise to the compiler that for the
scope of the pointer, the target of the pointer will only
be accessed through that pointer (and pointers copied
from it).
In C++ compilers that support it i...
Multiple Models in a single django ModelForm?
...
But how? Usually a FormView only has a single form_class assigned to it.
– erikbwork
Oct 7 '16 at 17:42
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Append an object to a list in R in amortized constant time, O(1)?
...irthday. Some kind readers keep repeating any shortcomings with it, so by all means also see some of the comments below. One suggestion for list types:
newlist <- list(oldlist, list(someobj))
In general, R types can make it hard to have one and just one idiom for all types and uses.
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Count number of records returned by group by
...his to DISTINCT COUNT() OVER(), and the query performance improved dramatically.
– Joe Aldrich
Sep 20 '17 at 13:33
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show 3 more comments
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What's the bad magic number error?
...the pyc file or trying to run a pyc from a different version of python (usually later) than your interpreter.
If they are your pyc files, just delete them and let the interpreter re-compile the py files. On UNIX type systems, that could be something as simple as:
rm *.pyc
or:
find . -name '*.py...
How to check a string for specific characters?
...r other characters.
... or
pattern = re.compile(r'\d\$,')
if pattern.findall(s):
print('Found')
else
print('Not found')
... or
chars = set('0123456789$,')
if any((c in chars) for c in s):
print('Found')
else:
print('Not Found')
[Edit: added the '$' in s answers]
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What is a “callable”?
...t's clear what a metaclass is , there is an associated concept that I use all the time without knowing what it really means.
...