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How to extract numbers from a string and get an array of ints?
...p = Pattern.compile("-?\\d+");
Matcher m = p.matcher("There are more than -2 and less than 12 numbers here");
while (m.find()) {
System.out.println(m.group());
}
... prints -2 and 12.
-? matches a leading negative sign -- optionally. \d matches a digit, and we need to write \ as \\ in a Java ...
Index all *except* one item in python
...lement:
a = range(10)[::-1] # [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
b = [x for i,x in enumerate(a) if i!=3] # [9, 8, 7, 5, 4, 3, 2, 1, 0]
This is very general, and can be used with all iterables, including numpy arrays. If you replace [] with (), b will be an iterator instead of...
echo that outputs to stderr
...
You could do this, which facilitates reading:
>&2 echo "error"
>&2 copies file descriptor #2 to file descriptor #1. Therefore, after this redirection is performed, both file descriptors will refer to the same file: the one file descriptor #2 was originally referri...
Pairs from single list
...
52
My favorite way to do it:
from itertools import izip
def pairwise(t):
it = iter(t)
ret...
Testing whether a value is odd or even
...
22 Answers
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What is the most efficient/elegant way to parse a flat table into a tree?
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462
Now that MySQL 8.0 supports recursive queries, we can say that all popular SQL databases support...
Python Dictionary Comprehension
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528
There are dictionary comprehensions in Python 2.7+, but they don't work quite the way you're tr...
How can I match a string with a regex in Bash?
...ite a bash script that contains a function so when given a .tar , .tar.bz2 , .tar.gz etc. file it uses tar with the relevant switches to decompress the file.
...
Fast permutation -> number -> permutation mapping algorithms
I have n elements. For the sake of an example, let's say, 7 elements, 1234567. I know there are 7! = 5040 permutations possible of these 7 elements.
...
How do I use .toLocaleTimeString() without displaying seconds?
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325
You can always set the options, based on this page you can set, to get rid of the seconds, some...