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Extract subset of key-value pairs from Python dictionary object?
... that you know the keys are going to be in the dictionary - see his answer if you aren't able to make that assumption. Alternatively, as timbo points out in the comments, if you want a key that's missing in bigdict to map to None, you can do:
{k: bigdict.get(k, None) for k in ('l', 'm', 'n')}
If...
How to check iOS version?
I want to check if the iOS version of the device is greater than 3.1.3
I tried things like:
37 Answers
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Can someone copyright a SQL query? [closed]
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If I were you, I would write a full description of what the query needs to do, including all the tables, fieldnames etc., and post that here. Someone here is bound to be able to write a new version of the query that is not co...
How can I determine the direction of a jQuery scroll event?
...= 0;
$(window).scroll(function(event){
var st = $(this).scrollTop();
if (st > lastScrollTop){
// downscroll code
} else {
// upscroll code
}
lastScrollTop = st;
});
share
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`elif` in list comprehension conditionals
Can we use elif in list comprehension?
6 Answers
6
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Does the ternary operator exist in R?
... asks, is there a control sequence in R similar to C's ternary operator ? If so, how do you use it? Thanks!
7 Answers
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Get the first item from an iterable that matches a condition
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In Python 2.6 or newer:
If you want StopIteration to be raised if no matching element is found:
next(x for x in the_iterable if x > 3)
If you want default_value (e.g. None) to be returned instead:
next((x for x in the_iterable if x > 3), d...
Python list subtraction operation
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Use a list comprehension:
[item for item in x if item not in y]
If you want to use the - infix syntax, you can just do:
class MyList(list):
def __init__(self, *args):
super(MyList, self).__init__(args)
def __sub__(self, other):
return self.__c...
Finding all possible combinations of numbers to reach a given sum
...subset_sum(numbers, target, partial=[]):
s = sum(partial)
# check if the partial sum is equals to target
if s == target:
print "sum(%s)=%s" % (partial, target)
if s >= target:
return # if we reach the number why bother to continue
for i in range(len(numbers...
If list index exists, do X
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I need to code such that if a certain list index exists, then run a function.
This is the perfect use for a try block:
ar=[1,2,3]
try:
t=ar[5]
except IndexError:
print('sorry, no 5')
# Note: this only is a valid test in this context
#...