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Convert column classes in data.table
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105
For a single column:
dtnew <- dt[, Quarter:=as.character(Quarter)]
str(dtnew)
Classes ‘...
Difference between doseq and for in Clojure
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168
The difference is that for builds a lazy sequence and returns it while doseq is for executing ...
Suppress/ print without b' prefix for bytes in Python 3
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111
Use decode:
print(curses.version.decode())
# 2.2
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Array to Hash Ruby
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a = ["item 1", "item 2", "item 3", "item 4"]
h = Hash[*a] # => { "item 1" => "item 2", "item 3" => "item 4" }
That's it. The * is called the splat operator.
One caveat per @Mike Lewis (in the comments): "Be very careful with...
promise already under evaluation: recursive default argument reference or earlier problems?
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164
Formal arguments of the form x=x cause this. Eliminating the two instances where they occur w...
Rails mapping array of hashes onto single hash
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163
You could compose Enumerable#reduce and Hash#merge to accomplish what you want.
input = [{"te...
How to match all occurrences of a regex
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edited May 18 '12 at 6:23
Andrew Marshall
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Getting the count of unique values in a column in bash
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153
To see a frequency count for column two (for example):
awk -F '\t' '{print $2}' * | sort | un...
Numpy array dimensions
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513
It is .shape:
ndarray.shape
Tuple of array dimensions.
Thus:
>>> a.shape
(2, ...
How to concatenate strings with padding in sqlite
...can follow along (basically what I proposed) here: http://verysimple.com/2010/01/12/sqlite-lpad-rpad-function/
-- the statement below is almost the same as
-- select lpad(mycolumn,'0',10) from mytable
select substr('0000000000' || mycolumn, -10, 10) from mytable
-- the statement below is almost t...