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Should import statements always be at the top of a module?
...t that's only paid once.
Putting the imports within a function will cause calls to that function to take longer.
So if you care about efficiency, put the imports at the top. Only move them into a function if your profiling shows that would help (you did profile to see where best to improve perform...
How can I count the occurrences of a list item?
...1, 4, 1].count(1)
3
Don't use this if you want to count multiple items. Calling count in a loop requires a separate pass over the list for every count call, which can be catastrophic for performance. If you want to count all items, or even just multiple items, use Counter, as explained in the othe...
How to read/process command line arguments?
I am originally a C programmer. I have seen numerous tricks and "hacks" to read many different arguments.
17 Answers
...
Numpy: find first index of value fast
...ments it. If you use anaconda python distribution it should already be installed.
The code will be compiled so it will be fast.
@jit(nopython=True)
def find_first(item, vec):
"""return the index of the first occurence of item in vec"""
for i in xrange(len(vec)):
if item == vec[i]:
...
Standard alternative to GCC's ##__VA_ARGS__ trick?
...
It is possible to avoid the use of GCC's ,##__VA_ARGS__ extension if you are willing to accept some hardcoded upper limit on the number of arguments you can pass to your variadic macro, as described in Richard Hansen's answer to this question. If you do not want to hav...
Getting attributes of a class
...gt;> inspect.getmembers(MyClass, lambda a:not(inspect.isroutine(a)))
[('__class__', type),
('__dict__',
<dictproxy {'__dict__': <attribute '__dict__' of 'MyClass' objects>,
'__doc__': None,
'__module__': '__main__',
'__weakref__': <attribute '__weakref__' of 'MyClass' obje...
C dynamically growing array
...ynamic array implementations work by starting off with an array of some (small) default size, then whenever you run out of space when adding a new element, double the size of the array. As you can see in the example below, it's not very difficult at all: (I've omitted safety checks for brevity)
type...
How to make MySQL handle UTF-8 properly
... My understanding is that utf8 within MySQL only refers to a small subset of full Unicode. You should use utf8mb4 instead to force full support. See mathiasbynens.be/notes/mysql-utf8mb4 "For a long time, I was using MySQL’s utf8 charset for databases, tables, and columns, assuming i...
Why does sudo change the PATH?
...
Yeah, but it's totally counterintuitive. It probably fools the good guys more than the bad guys.
– Brian Armstrong
Jun 20 '09 at 2:24
...
libpng warning: iCCP: known incorrect sRGB profile
...geMagick's
convert in.png out.png
To remove the invalid iCCP chunk from all of the PNG files in a folder (directory), you can use mogrify from ImageMagick:
mogrify *.png
This requires that your ImageMagick was built with libpng16. You can easily check it by running:
convert -list format | gre...