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Understanding dict.copy() - shallow or deep?
...pied by value, but just creating a new reference.
>>> a = {1: [1,2,3]}
>>> b = a.copy()
>>> a, b
({1: [1, 2, 3]}, {1: [1, 2, 3]})
>>> a[1].append(4)
>>> a, b
({1: [1, 2, 3, 4]}, {1: [1, 2, 3, 4]})
In contrast, a deep copy will copy all contents by valu...
Mean per group in a data.frame [duplicate]
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257
This type of operation is exactly what aggregate was designed for:
d <- read.table(text=
'...
Sorting multiple keys with Unix sort
...
Use the -k option (or --key=POS1[,POS2]). It can appear multiple times and each key can have global options (such as n for numeric sort)
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Check if two unordered lists are equal [duplicate]
...Counter(x) == collections.Counter(y)
>>>
>>> compare([1,2,3], [1,2,3,3])
False
>>> compare([1,2,3], [1,2,3])
True
>>> compare([1,2,3,3], [1,2,2,3])
False
>>>
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WinDBG用法详解 PDF - 文档下载 - 清泛网 - 专注C/C++及内核技术
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30.1.2内容............................................................................................................................2
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How do I get both STDOUT and STDERR to go to the terminal and a log file?
...shell you use, you first have to redirect stderr to stdout using
./a.out 2>&1 | tee output
or
./a.out |& tee output
In csh, there is a built-in command called "script" that will capture everything that goes to the screen to a file. You start it by typing "script", then doing what...
What's the difference between RANK() and DENSE_RANK() functions in oracle?
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248
RANK gives you the ranking within your ordered partition. Ties are assigned the same rank, wit...
Why can't R's ifelse statements return vectors?
...st vectors, you will get longer results:
> ifelse(c(TRUE, FALSE), c(1, 2), c(3, 4))
[1] 1 4
So ifelse is intended for the specific purpose of testing a vector of booleans and returning a vector of the same length, filled with elements taken from the (vector) yes and no arguments.
It is a comm...
How to find the kth largest element in an unsorted array of length n in O(n)?
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