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Why does [5,6,8,7][1,2] = 8 in JavaScript?
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3 Answers
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How to concatenate twice with the C preprocessor and expand a macro as in “arg ## _ ## MACRO”?
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Standard C Preprocessor
$ cat xx.c
#define VARIABLE 3
#define PASTER(x,y) x ## _ ## y
#define EVALUATOR(x,y) PASTER(x,y)
#define NAME(fun) EVALUATOR(fun, VARIABLE)
extern void NAME(mine)(char *x);
$ gcc -E xx.c
# 1 "xx.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1...
Find the max of two or more columns with pandas
...>>> import pandas as pd
>>> df = pd.DataFrame({"A": [1,2,3], "B": [-2, 8, 1]})
>>> df
A B
0 1 -2
1 2 8
2 3 1
>>> df[["A", "B"]]
A B
0 1 -2
1 2 8
2 3 1
>>> df[["A", "B"]].max(axis=1)
0 1
1 8
2 3
and so:
>>> df["C"] = ...
How to get a specific output iterating a hash in Ruby?
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328
hash.each do |key, array|
puts "#{key}-----"
puts array
end
Regarding order I should add...
Paste multiple columns together
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# your starting data..
data <- data.frame('a' = 1:3, 'b' = c('a','b','c'), 'c' = c('d', 'e', 'f'), 'd' = c('g', 'h', 'i'))
# columns to paste together
cols <- c( 'b' , 'c' , 'd' )
# create a new column `x` with the three columns collapsed together
data$x <- apply( d...
Shuffle two list at once with same order
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You can do it as:
import random
a = ['a', 'b', 'c']
b = [1, 2, 3]
c = list(zip(a, b))
random.shuffle(c)
a, b = zip(*c)
print a
print b
[OUTPUT]
['a', 'c', 'b']
[1, 3, 2]
Of course, this was an example with simpler lists, but the adaptation will be the same for your case.
Hope it ...
How to slice an array in Bash
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317
See the Parameter Expansion section in the Bash man page. A[@] returns the contents of the arr...
How to sort Counter by value? - python
...;> from collections import Counter
>>> x = Counter({'a':5, 'b':3, 'c':7})
>>> x.most_common()
[('c', 7), ('a', 5), ('b', 3)]
It'll do so in the most efficient manner possible; if you ask for a Top N instead of all values, a heapq is used instead of a straight sort:
>>&g...
Python using enumerate inside list comprehension
...t that gets returned is as expected:
> [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]
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How to swap keys and values in a hash
... (in essence, by letting you access keys through values):
{a: 1, b: 2, c: 3}.key(1)
=> :a
If you want to keep the inverted hash, then Hash#invert should work for most situations:
{a: 1, b: 2, c: 3}.invert
=> {1=>:a, 2=>:b, 3=>:c}
BUT...
If you have duplicate values, invert will...