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In pure functional languages, is there an algorithm to get the inverse function?
...Daniel Wagner
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3
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Python 3: UnboundLocalError: local variable referenced before assignment [duplicate]
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Jakob BowyerJakob Bowyer
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Using sed to mass rename files
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answered Mar 3 '10 at 15:55
Edward AndersonEdward Anderson
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Split delimited strings in a column and insert as new rows [duplicate]
...her way of doing it..
df <- read.table(textConnection("1|a,b,c\n2|a,c\n3|b,d\n4|e,f"), header = F, sep = "|", stringsAsFactors = F)
df
## V1 V2
## 1 1 a,b,c
## 2 2 a,c
## 3 3 b,d
## 4 4 e,f
s <- strsplit(df$V2, split = ",")
data.frame(V1 = rep(df$V1, sapply(s, length)), V2 = ...
What is an idempotent operation?
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answered Jul 3 '09 at 1:10
Greg HewgillGreg Hewgill
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Getting a list of all subdirectories in the current directory
...ectory)
will yield a tuple for each subdirectory. Ths first entry in the 3-tuple is a directory name, so
[x[0] for x in os.walk(directory)]
should give you all of the subdirectories, recursively.
Note that the second entry in the tuple is the list of child directories of the entry in the first...
How to get all of the immediate subdirectories in Python
...l sorting (1, 2, 10), please have a look at https://stackoverflow.com/a/48030307/2441026
Results:
scandir is: 3x faster than walk, 32x faster than listdir (with filter), 35x faster than Pathlib and 36x faster than listdir and 37x (!) faster than glob.
Scandir: 0.977
Walk: ...
Move capture in lambda
...et, but with some tricks that involve helper types. Fortunately, the Clang 3.4 compiler already implements this awesome feature. The compiler will be released December 2013 or January 2014, if the recent release pace will be kept.
UPDATE: The Clang 3.4 compiler was released on 6 Jan 2014 with the ...
Use of .apply() with 'new' operator. Is this possible?
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36 Answers
36
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Fastest way to replace NAs in a large data.table
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system.time(a_gdata = f_gdata(dt1))
user system elapsed
18.805 12.301 134.985
system.time(a_andrie = f_andrie(dt1))
Error: cannot allocate vector of size 305.2 Mb
Timing stopped at: 14.541 7.764 68.285
system.time(f_dowle(dt1))
user system elapsed
7.452 4.144 19.590 # EDIT h...