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Cartesian product of multiple arrays in JavaScript
...overly complicated, most of them take 20 lines of code or even more.
This example uses just two lines of vanilla JavaScript, no lodash, underscore or other libraries:
let f = (a, b) => [].concat(...a.map(a => b.map(b => [].concat(a, b))));
let cartesian = (a, b, ...c) => b ? cartesian(f(...
Pandas dataframe get first row of each group
...If you need id as column:
>>> df.groupby('id').first().reset_index()
id value
0 1 first
1 2 first
2 3 first
3 4 second
4 5 first
5 6 first
6 7 fourth
To get n first records, you can use head():
>>> df.groupby('id').head(2).reset_index(drop=True)
...
How can I implement prepend and append with regular JavaScript?
...ild)
Inserts the node newChild as a child of parentNode before the
existing child node refChild. (Returns newChild.)
If refChild is null, newChild is added at the end of the list of
children. Equivalently, and more readably, use
parentNode.appendChild(newChild).
...
Is calculating an MD5 hash less CPU intensive than SHA family functions?
...ng an MD5 hash less CPU intensive than SHA-1 or SHA-2 on "standard" laptop x86 hardware? I'm interested in general information, not specific to a certain chip.
...
correct way to use super (argument passing)
...s following Python's Super Considered Harmful , and went to test out his examples.
3 Answers
...
Remove specific commit
... be a toss up between revert and rebase, and there are no straightforward examples, and the docs assume I know more than I do.
...
Filter rows which contain a certain string
...lready posted by the @latemail in the comments above. You can use regular expressions for the second and subsequent arguments of filter like this:
dplyr::filter(df, !grepl("RTB",TrackingPixel))
Since you have not provided the original data, I will add a toy example using the mtcars data set. Imag...
What is the difference between return and return()?
... is, nothing. The parentheses are allowed because they are allowed in any expression to influence evaluation order, but in your examples they're just superfluous.
return is not a function, but a statement. It is syntactically similar to other simple control flow statements like break and continue t...
Object of custom type as dictionary key
..._(self, other):
# Not strictly necessary, but to avoid having both x==y and x!=y
# True at the same time
return not(self == other)
The Python dict documentation defines these requirements on key objects, i.e. they must be hashable.
...
Is there a way to 'uniq' by column?
...field 1
Test result:
overflow@domain2.com,2009-11-27 00:58:29.793000000,xx3.net,255.255.255.0
stack2@domain.com,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
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