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How can I get nth element from a list?
...ly then below is one way to do it:
dataAt :: Int -> [a] -> a
dataAt _ [] = error "Empty List!"
dataAt y (x:xs) | y <= 0 = x
| otherwise = dataAt (y-1) xs
share
|
improve...
Django. Override save for model
...
Some thoughts:
class Model(model.Model):
_image=models.ImageField(upload_to='folder')
thumb=models.ImageField(upload_to='folder')
description=models.CharField()
def set_image(self, val):
self._image = val
self._image_changed = True
...
Get file name from URL
...
If you let String url = new URL(original_url).getPath() and add a special case for filenames that don't contain a . then this works fine.
– Jason C
May 6 '15 at 20:28
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How exactly does a generator comprehension work?
...s, and yields each item out of the expression, one by one.
>>> my_list = [1, 3, 5, 9, 2, 6]
>>> filtered_list = [item for item in my_list if item > 3]
>>> print(filtered_list)
[5, 9, 6]
>>> len(filtered_list)
3
>>> # compare to generator expression
.....
What's an easy way to read random line from a file in Unix command line?
...from the Camel Book:
perl -e 'srand; rand($.) < 1 && ($line = $_) while <>; print $line;' file
This has a significant advantage in space over reading the whole file in. You can find a proof of this method in The Art of Computer Programming, Volume 2, Section 3.4.2, by Donald E. K...
Perl flags -pe, -pi, -p, -w, -d, -i, -t?
...ns (for most things):
$ perl -MO=Deparse -p -e 1
LINE: while (defined($_ = <ARGV>)) {
'???';
}
continue {
die "-p destination: $!\n" unless print $_;
}
-e syntax OK
1 is represented by '???', because it is optimized away.
$ perl -MO=Deparse -p -i -e 1
BEGIN { $^I = ""; }
LINE...
How to make rounded percentages add up to 100%
...sion using underscorejs:
function foo(l, target) {
var off = target - _.reduce(l, function(acc, x) { return acc + Math.round(x) }, 0);
return _.chain(l).
sortBy(function(x) { return Math.round(x) - x }).
map(function(x, i) { return Math.round(x) + (off > i) - (i &...
Python list of dictionaries search
... 3.6.4, W7x64.
from random import randint
from timeit import timeit
list_dicts = []
for _ in range(1000): # number of dicts in the list
dict_tmp = {}
for i in range(10): # number of keys for each dict
dict_tmp[f"key{i}"] = randint(0,50)
list_dicts.append( dict_tmp )
d...
Immutable vs Mutable types
... pass by value in C. A counterexample to your analogy is if you do def f(my_list): my_list = [1, 2, 3]. With pass-by-reference in C, the value of the argument could change by calling that function. In Python, that function doesn't do anything. def f(my_list): my_list[:] = [1, 2, 3] would do somethin...
How to get the anchor from the URL using jQuery?
...xOf() and .substring(), like this:
var url = "www.aaa.com/task1/1.3.html#a_1";
var hash = url.substring(url.indexOf("#")+1);
You can give it a try here, if it may not have a # in it, do an if(url.indexOf("#") != -1) check like this:
var url = "www.aaa.com/task1/1.3.html#a_1", idx = url.indexOf("...