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How to select rows from a DataFrame based on column values?
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10 Answers
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Fastest way to determine if an integer's square root is an integer
...ts. (I found looking at the last six didn't help.) I also answer yes for 0. (In reading the code below, note that my input is int64 x.)
if( x < 0 || (x&2) || ((x & 7) == 5) || ((x & 11) == 8) )
return false;
if( x == 0 )
return true;
Next, check if it's a square modulo 25...
C char array initialization
... how you initialize an array, but for:
The first declaration:
char buf[10] = "";
is equivalent to
char buf[10] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
The second declaration:
char buf[10] = " ";
is equivalent to
char buf[10] = {' ', 0, 0, 0, 0, 0, 0, 0, 0, 0};
The third declaration:
char buf[...
Modifying a subset of rows in a pandas dataframe
...fy this DataFrame (or create a copy) so that B is always NaN whenever A is 0. How would I achieve that?
5 Answers
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Why does ++[[]][+[]]+[+[]] return the string “10”?
This is valid and returns the string "10" in JavaScript ( more examples here ):
9 Answers
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What is the most pythonic way to check if an object is a number?
...cimal import Decimal
... from fractions import Fraction
... for n in [2, 2.0, Decimal('2.0'), complex(2, 0), Fraction(2, 1), '2']:
... print(f'{n!r:>14} {isinstance(n, Number)}')
2 True
2.0 True
Decimal('2.0') True
(2+0j) True
Fraction(2, 1) True
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Most efficient way to create a zero filled JavaScript array?
...duces Array.prototype.fill. It can be used like this:
new Array(len).fill(0);
Not sure if it's fast, but I like it because it's short and self-describing.
It's still not in IE (check compatibility), but there's a polyfill available.
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Why does the expression 0 < 0 == 0 return False in Python?
... make range comparisons easy to express. It's much nicer to be able to say 0 &lt; x &lt;= 5 than to say (0 &lt; x) and (x &lt;= 5).
These are called chained comparisons. And that's a link to the documentation for them.
With the other cases you talk about, the parenthesis force one relational opera...
How can I check if an ip is in a network in Python?
Given an ip address (say 192.168.0.1), how do I check if it's in a network (say 192.168.0.0/24) in Python?
27 Answers
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How to validate an e-mail address in swift?
...ValidEmail(_ email: String) -&gt; Bool {
let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
let emailPred = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
return emailPred.evaluate(with: email)
}
for versions of Swift earlier than 3.0:
func isValidEmail(e...