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What does the ^ operator do in Java?
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422
The ^ operator in Java
^ in Java is the exclusive-or ("xor") operator.
Let's take 5^6 as exam...
`elif` in list comprehension conditionals
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259
Python's conditional expressions were designed exactly for this sort of use-case:
>>>...
pandas GroupBy columns with NaN (missing) values
...e groupby (e.g. -1):
In [11]: df.fillna(-1)
Out[11]:
a b
0 1 4
1 2 -1
2 3 6
In [12]: df.fillna(-1).groupby('b').sum()
Out[12]:
a
b
-1 2
4 1
6 3
That said, this feels pretty awful hack... perhaps there should be an option to include NaN in groupby (see this github issue ...
Operation on every pair of element in a list
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233
Check out product() in the itertools module. It does exactly what you describe.
import itert...
Running a cron job at 2:30 AM everyday
How to configure a cron job to run every night at 2:30? I know how to make it run at 2, but not 2:30.
6 Answers
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How to compare two strings in dot separated version format in Bash?
Is there any way to compare such strings on bash, e.g.: 2.4.5 and 2.8 and 2.4.5.1 ?
29 Answers
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What is the difference between tinyint, smallint, mediumint, bigint and int in MySQL?
...ation:
MySQL
Postgres
Oracle (they just have a NUMBER datatype really)
DB2
Turns out they all use the same specification (with a few minor exceptions noted below) but support various combinations of those types (Oracle not included because it has just a NUMBER datatype, see the above link):
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Flatten an Array of Arrays in Swift
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Swift >= 3.0
reduce:
let numbers = [[1,2,3],[4],[5,6,7,8,9]]
let reduced = numbers.reduce([], +)
flatMap:
let numbers = [[1,2,3],[4],[5,6,7,8,9]]
let flattened = numbers.flatMap { $0 }
joined:
let numbers = [[1,2,3],[4],[5,6,7,8,9]]
let joined = Array(number...
Select multiple columns in data.table by their numeric indices
...llowing all just work:
library(data.table)
dt <- data.table(a = 1, b = 2, c = 3)
# select single column by index
dt[, 2]
# b
# 1: 2
# select multiple columns by index
dt[, 2:3]
# b c
# 1: 2 3
# select single column by name
dt[, "a"]
# a
# 1: 1
# select multiple columns by name
dt[, ...