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Creating an R dataframe row-by-row
...then during your operations insert row at a time
DF[i, ] <- list(1.4, "foo")
That should work for arbitrary data.frame and be much more efficient. If you overshot N you can always shrink empty rows out at the end.
sha...
It is more efficient to use if-return-return or if-else-return?
...
From Chromium's style guide:
Don't use else after return:
# Bad
if (foo)
return 1
else
return 2
# Good
if (foo)
return 1
return 2
return 1 if foo else 2
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Access nested dictionary items via a list of keys?
... _element = _element[key]
_element[keys[-1]] = value
example = {"foo": { "bar": { "baz": "ok" } } }
keys = ['foo', 'bar']
nested_set(example, "yay", *keys)
print(example)
Output
{'foo': {'bar': 'yay'}}
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How to put multiple statements in one line?
...of simple statements, separated by semi-colon:
for i in range(10): print "foo"; print "bar"
But as soon as you add a construct that introduces an indented block (like if), you need the line break. Also,
for i in range(10): print "i equals 9" if i==9 else None
is legal and might approximate wha...
Can PostgreSQL index array columns?
...e to index the individual array elements. For example:
CREATE TABLE test (foo int[]);
INSERT INTO test VALUES ('{1,2,3}');
INSERT INTO test VALUES ('{4,5,6}');
CREATE INDEX test_index on test ((foo[1]));
SET enable_seqscan TO off;
EXPLAIN ANALYZE SELECT * from test WHERE foo[1]=1;
...
Programmatically select text in a contenteditable HTML element?
...AllRanges();
sel.addRange(range);
}
var el = document.getElementById("foo");
selectElementContents(el);
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Please explain some of Paul Graham's points on Lisp
...as str])
;; this is the interesting bit:
(println (str/replace-re #"\d+" "FOO" "a123b4c56"))
This snippet of Clojure code prints out aFOObFOOcFOO. Note that Clojure arguably does not fully satisfy the fourth point on your list, since read-time is not really open to user code; I will discuss what i...
WITH CHECK ADD CONSTRAINT followed by CHECK CONSTRAINT vs. ADD CONSTRAINT
...t new data, new constraints. If you disable a constraint with ALTER TABLE foo NOCHECK CONSTRAINT fk_b and then re-enable it with ALTER TABLE foo CHECK CONSTRAINT fk_b it doesn't verify the constraint. ALTER TABLE foo WITH CHECK CHECK CONSTRAINT fk_b is necessary in order to have the data verified....
How do I convert a String object into a Hash object?
..."first second > third"=>"first second > third", "after comma > foo"=>:symbolvalue, "another after comma > foo"=>10}, "bravo"=>{:symbol=>:symbolvalue, :aftercomma=>10, :anotheraftercomma=>"first second > third"}, "charlie"=>{1=>10, 2=>"first second > th...
How can I use “sizeof” in a preprocessor macro?
...macro:
/*
* Simple compile time assertion.
* Example: CT_ASSERT(sizeof foo <= 16, foo_can_not_exceed_16_bytes);
*/
#define CT_ASSERT(exp, message_identifier) \
struct compile_time_assertion { \
char message_identifier : 8 + !(exp); \
}
For example in comment MSVC tells some...