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insert vs emplace vs operator[] in c++ map
I'm using maps for the first time and I realized that there are many ways to insert an element. You can use emplace() , operator[] or insert() , plus variants like using value_type or make_pair . While there is a lot of information about all of them and questions about particular cases, I sti...
How do I get a class instance of generic type T?
...
The short answer is, that there is no way to find out the runtime type of generic type parameters in Java. I suggest reading the chapter about type erasure in the Java Tutorial for more details.
A popular solution to this is to pass the Class of the type parameter into the constructor...
Decorators with parameters?
...ep
@types(str, int) # arg1 is str, arg2 is int
def string_multiply(text, times):
return text * times
print(string_multiply('hello', 3)) # Prints hellohellohello
print(string_multiply(3, 3)) # Fails miserably with TypeError
A final note: here I'm not using functools.wraps for the...
Python mysqldb: Library not loaded: libmysqlclient.18.dylib
...s in your source files.
Also compared to yoshisurfs answer, most of the time when mysql gets installed the mysql directory should be renamed to just mysql, not the whole file name, for ease of use.
export DYLD_LIBRARY_PATH=/usr/local/mysql/lib:$DYLD_LIBRARY_PATH
...
How to detect if a script is being sourced
...estfile.ksh:
cat >testfile.ksh
chmod +x testfile.ksh
Than run it two time:
./testfile.ksh
. ./testfile.ksh
ls -l /tmp/ksh-*.log
-rw-r--r-- 1 user user 2183 avr 11 13:48 /tmp/ksh-9725.log
-rw-r--r-- 1 user user 2140 avr 11 13:48 /tmp/ksh-9781.log
echo $$
9725
and see:
diff /tmp/ksh-{9...
multiprocessing: sharing a large read-only object between processes?
...objects could be pickled Python objects to save a tiny bit of file reading time.
Write a startup program that (1) reads your original gigantic object and writes a page-structured, byte-coded file using seek operations to assure that individual sections are easy to find with simple seeks. This is wh...
Extending the User model with custom fields in Django
...OFILE_MODULE = 'YOURAPP.UserProfile'
This will create a userprofile each time a user is saved if it is created.
You can then use
user.get_profile().whatever
Here is some more info from the docs
http://docs.djangoproject.com/en/dev/topics/auth/#storing-additional-information-about-users
Upd...
Principal component analysis in Python
...g signal is a sinusoidally modulated image
img = lena()
t = np.arange(100)
time = np.sin(0.1*t)
real = time[:,np.newaxis,np.newaxis] * img[np.newaxis,...]
# we add some noise
noisy = real + np.random.randn(*real.shape)*255
# (observations, features) matrix
M = noisy.reshape(noisy.shape[0],-1)
# s...
From io.Reader to string in Go
...I can't imagine a scenario where transmission latency won't be a squillion times larger than the trivial time it takes to copy the byte array. Any functional language copies this type of immutable stuff around all over the place, and still runs plenty fast.
– see sharper
...
Best practices for circular shift (rotate) operations in C++
... MIPS that only provide a rotate-right. (This optimizes away with compile-time-constant counts.)
Fun fact: ARM doesn't really have dedicated shift/rotate instructions, it's just MOV with the source operand going through the barrel-shifter in ROR mode: mov r0, r0, ror r1. So a rotate can fold into...