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Fast way of counting non-zero bits in positive integer
...1") is the fastest I could find in pure Python.
I tried adapting Óscar's and Adam's solutions to process the integer in 64-bit and 32-bit chunks, respectively. Both were at least ten times slower than bin(n).count("1") (the 32-bit version took about half again as much time).
On the other hand, gm...
How to put multiple statements in one line?
...t is not possible with Python (which makes Python close to useless for command-line one-liner programs). Even explicit use of parentheses does not avoid the syntax exception. You can get away with a sequence of simple statements, separated by semi-colon:
for i in range(10): print "foo"; print "bar"...
Base64 length calculation?
... * 6 = 24 bits = 3 bytes.
So you need 4*(n/3) chars to represent n bytes, and this needs to be rounded up to a multiple of 4.
The number of unused padding chars resulting from the rounding up to a multiple of 4 will obviously be 0, 1, 2 or 3.
...
Remove trailing newline from the elements of a string list
... could I then just say stripped_list = map(str.strip, my_list) and then print stripped_list to print this new list?
– George Burrows
Nov 2 '11 at 17:02
19
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What does “O(1) access time” mean?
...een this term "O(1) access time" used to mean "quickly" but I don't understand what it means. The other term that I see with it in the same context is "O(n) access time". Could someone please explain in a simple way what these terms mean?
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Extracting the last n characters from a string in R
...se R, but it's straight-forward to make a function to do this using substr and nchar:
x <- "some text in a string"
substrRight <- function(x, n){
substr(x, nchar(x)-n+1, nchar(x))
}
substrRight(x, 6)
[1] "string"
substrRight(x, 8)
[1] "a string"
This is vectorised, as @mdsumner point...
Regex exactly n OR m times
...ou are doing it is fine.
An alternative is:
X{m}(X{k})?
where m < n and k is the value of n-m.
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What is the exact meaning of IFS=$'\n'?
...ot exactly so -- \n is just an (escaped) letter n. You are right that '\n' and "\n" are backlash followed by n.
– Roman Cheplyaka
Nov 8 '10 at 23:08
15
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How to change to an older version of Node.js
...
One way is to use NVM, the Node Version Manager.
Use following command to get nvm
curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.34.0/install.sh | bash
You can find it at https://github.com/creationix/nvm
It allows you to easily install and manage multiple versions of node...
Algorithm to generate all possible permutations of a list?
... left to right, all the permutations of the remaining items are generated (and each one is added with the current elements). This can be done recursively (or iteratively if you like pain) until the last item is reached at which point there is only one possible order.
So with the list [1,2,3,4] all ...