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How does git compute file hashes?
... | shasum
8ab686eafeb1f44702738c8b0f24f2567c36da6d
Source: http://alblue.bandlem.com/2011/08/git-tip-of-week-objects.html
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How to find all serial devices (ttyS, ttyUSB, ..) on Linux without opening them?
...ll TTY devices but you might want to exclude those pesky virtual terminals and pseudo terminals. I suggest you examine only those which have a device/driver entry:
# ll /sys/class/tty/*/device/driver
lrwxrwxrwx 1 root root 0 2012-03-28 19:07 /sys/class/tty/ttyS0/device/driver -> ../../../bus/pnp...
Converting a list to a set changes element order
...at when I am converting a list to set the order of elements is changed and is sorted by character.
11 Answers
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Round to 5 (or other number) in Python
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I don't know of a standard function in Python, but this works for me:
Python 2
def myround(x, base=5):
return int(base * round(float(x)/base))
Python3
def myround(x, base=5):
return base * round(x/base)
It is easy to see why the a...
Data structure: insert, remove, contains, get random element, all at O(1)
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Consider a data structure composed of a hashtable H and an array A. The hashtable keys are the elements in the data structure, and the values are their positions in the array.
insert(value): append the value to array and let i be its index in A. Set H[value]=i.
remove(value)...
Python list subtraction operation
...set(x) - set(y))
>>> z
[0, 8, 2, 4, 6]
Or you might just have x and y be sets so you don't have to do any conversions.
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How do I upgrade my ruby 1.9.2-p0 to the latest patch level using rvm?
...2.
Finally, to install the new ruby version, just run rvm install 1.9.2 - and wait for it to compile!
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MySQL DISTINCT on a GROUP_CONCAT()
...n a string like:
test1 test2 test3 test1 test3 test4
(notice that test1 and test3 are duplicated) while the OP wants to return this string:
test1 test2 test3 test4
the problem here is that the string "test1 test3" is duplicated and is inserted only once, but all of the others are distinct to e...
Is there a performance difference between a for loop and a for-each loop?
... The for-each loop, introduced in
release 1.5, gets rid of the clutter
and the opportunity for error by
hiding the iterator or index variable
completely. The resulting idiom
applies equally to collections and
arrays:
// The preferred idiom for iterating over collections and arrays
for (...
How can I join elements of an array in Bash?
...a #a
The code above is based on the ideas by @gniourf_gniourf, @AdamKatz, and @MattCowell.
Alternatively, a simpler function that supports only single character delimiter, would be:
function join_by { local IFS="$1"; shift; echo "$*"; }
For example,
join_by , a "b c" d #a,b c,d
join_by / var local...