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How to change the opacity (alpha, transparency) of an element in a canvas element after it has been
... seem to affect image drawing.
//works with shapes but not with images
ctx.fillStyle = "rgba(255, 255, 255, 0.5)";
I have concluded that setting the globalCompositeOperation works with images.
//works with images
ctx.globalCompositeOperation = "lighter";
I wonder if there is some kind third ...
How to install mongoDB on windows?
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On a side note Windows XP support is discontinued from v2.2+ docs.mongodb.org/manual/release-notes/2.2/…
– Prashant Bhate
Aug 31 '12 at 11:40
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How to get all subsets of a set? (powerset)
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The Python itertools page has exactly a powerset recipe for this:
from itertools import chain, combinations
def powerset(iterable):
"powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
s = list(iterable)
return chain.from_it...
What do you call the -> operator in Ruby?
...s"), a lambda defined using -> is called lambda literal.
succ = ->(x){ x+1 }
succ.call(2)
The code is equivalent to the following one.
succ = lambda { |x| x + 1 }
succ.call(2)
Informally, I have heard it being called stabby lambda or stabby literal.
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Get the index of the object inside an array, matching a condition
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As of 2016, you're supposed to use Array.findIndex (an ES2015/ES6 standard) for this:
a = [
{prop1:"abc",prop2:"qwe"},
{prop1:"bnmb",prop2:"yutu"},
{prop1:"zxvz",prop2:"qwrq"}];
index = a.findIndex(x => x.prop2 ==="yutu");
console.log(index);
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Why is parenthesis in print voluntary in Python 2.7?
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In Python 2.x print is actually a special statement and not a function*.
This is also why it can't be used like: lambda x: print x
Note that (expr) does not create a Tuple (it results in expr), but , does. This likely results in the co...
Why can't non-default arguments follow default arguments?
Why does this piece of code throw a SyntaxError?
4 Answers
4
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Relationship between SciPy and NumPy
...'s almost certainly a scipy.foo . Most of the time, the two appear to be exactly the same, oftentimes even pointing to the same function object.
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Find the nth occurrence of substring in a string
...that can't match the needle) one-liner:
'foo bar bar bar'.replace('bar', 'XXX', 1).find('bar')
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How can I trim leading and trailing white space?
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# Returns string without leading white space
trim.leading <- function (x) sub("^\\s+", "", x)
# Returns string without trailing white space
trim.trailing <- function (x) sub("\\s+$", "", x)
# Returns string without leading or trailing white space
trim <- function (x) gsub("^\\s+|\\s+$",...