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How do I find if a string starts with another string in Ruby?
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263
puts 'abcdefg'.start_with?('abc') #=> true
[edit] This is something I didn't know before...
SQL Logic Operator Precedence: And and Or
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296
And has precedence over Or, so, even if a <=> a1 Or a2
Where a And b
is not the same...
CPU Privilege Rings: Why rings 1 and 2 aren't used?
...of the modern protection model) only has a concept of privileged (ring 0,1,2) and unprivileged, the benefit to rings 1 and 2 were diminished greatly.
The intent by Intel in having rings 1 and 2 is for the OS to put device drivers at that level, so they are privileged, but somewhat separated from th...
How do I check the difference, in seconds, between two dates?
...ates, use total_seconds like this:
import datetime as dt
a = dt.datetime(2013,12,30,23,59,59)
b = dt.datetime(2013,12,31,23,59,59)
(b-a).total_seconds()
86400.0
#note that seconds doesn't give you what you want:
(b-a).seconds
0
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One-line list comprehension: if-else variants
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342
x if y else z is the syntax for the expression you're returning for each element. Thus you need:...
How to count the number of true elements in a NumPy bool array
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265
You have multiple options. Two options are the following.
numpy.sum(boolarr)
numpy.count_nonz...
Java 7 language features with Android
...lly without any patches. Try-with-resource requires API Level 19+, and NIO 2.0 stuff are missing.
If you can't use Java 7 features, see @Nuno's answer on how to edit your build.gradle.
The following is for historical interest only.
A small part of Java 7 can certainly be used with Android (not...
How to merge lists into a list of tuples?
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In Python 2:
>>> list_a = [1, 2, 3, 4]
>>> list_b = [5, 6, 7, 8]
>>> zip(list_a, list_b)
[(1, 5), (2, 6), (3, 7), (4, 8)]
In Python 3:
>>> list_a = [1, 2, 3, 4]
>>> list_b = [5, 6, 7, 8]...
Clojure: cons (seq) vs. conj (list)
...guments to insert into a collection, while cons takes just one:
(conj '(1 2 3) 4 5 6)
; => (6 5 4 1 2 3)
(cons 4 5 6 '(1 2 3))
; => IllegalArgumentException due to wrong arity
Another difference is in the class of the return value:
(class (conj '(1 2 3) 4))
; => clojure.lang.Persistent...
What's the difference between lists enclosed by square brackets and parentheses in Python?
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278
Square brackets are lists while parentheses are tuples.
A list is mutable, meaning you can ch...