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Finding the index of elements based on a condition using python list comprehension
... of a list.
>>> import numpy
>>> a = numpy.array([1, 2, 3, 1, 2, 3])
>>> a
array([1, 2, 3, 1, 2, 3])
>>> numpy.where(a > 2)
(array([2, 5]),)
>>> a > 2
array([False, False, True, False, False, True], dtype=bool)
>>> a[numpy.where(a > 2...
How to extend an existing JavaScript array with another array, without creating a new array
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1553
The .push method can take multiple arguments. You can use the spread operator to pass all the el...
Getting parts of a URL (Regex)
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153
A single regex to parse and breakup a
full URL including query parameters
and anchors e.g...
How to compare two floating point numbers in Bash?
...s in scientific format, provided a capital letter E is employed, e.g. num1=3.44E6
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How to make a flat list out of list of lists?
...e the timeit module in the standard library:
$ python -mtimeit -s'l=[[1,2,3],[4,5,6], [7], [8,9]]*99' '[item for sublist in l for item in sublist]'
10000 loops, best of 3: 143 usec per loop
$ python -mtimeit -s'l=[[1,2,3],[4,5,6], [7], [8,9]]*99' 'sum(l, [])'
1000 loops, best of 3: 969 usec per loo...
python pandas dataframe to dictionary
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answered Sep 9 '13 at 9:55
jorisjoris
94.6k3030 gold badges197197 silver badges171171 bronze badges
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unix - head AND tail of file
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answered Dec 24 '11 at 13:29
Aleksandra ZalcmanAleksandra Zalcman
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Why does substring slicing with index out of range work?
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3 Answers
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Do threads have a distinct heap?
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edited May 23 '17 at 10:31
Community♦
111 silver badge
answered Nov 3 '09 at 5:33
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Rails 3: Get Random Record
...NDOM()") # For MySQL :order => "RAND()", - thanx, @DanSingerman
# Rails 3
Thing.order("RANDOM()").first
or
Thing.first(:offset => rand(Thing.count))
# Rails 3
Thing.offset(rand(Thing.count)).first
Actually, in Rails 3 all examples will work. But using order RANDOM is quite slow for big ta...