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What is the most efficient string concatenation method in python?
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edited May 11 '16 at 7:04
Quentin Pradet
4,28622 gold badges2626 silver badges4040 bronze badges
answ...
Cocoa: What's the difference between the frame and the bounds?
...
908
The bounds of an UIView is the rectangle, expressed as a location (x,y) and size (width,height)...
How do I replace NA values with zeros in an R dataframe?
...nt in @gsk3 answer. A simple example:
> m <- matrix(sample(c(NA, 1:10), 100, replace = TRUE), 10)
> d <- as.data.frame(m)
V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
1 4 3 NA 3 7 6 6 10 6 5
2 9 8 9 5 10 NA 2 1 7 2
3 1 1 6 3 6 NA 1 4 1 6
4 NA 4 NA 7 10 2 NA 4 1...
What's the simplest way to test whether a number is a power of 2 in C++?
...
190
(n & (n - 1)) == 0 is best. However, note that it will incorrectly return true for n=0, so i...
Is “argv[0] = name-of-executable” an accepted standard or just a common convention?
When passing argument to main() in a C or C++ application, will argv[0] always be the name of the executable? Or is this just a common convention and not guaranteed to be true 100% of the time?
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Are members of a C++ struct initialized to 0 by default?
... constructors
struct Snapshot {
int x;
double y;
Snapshot():x(0),y(0) { }
// other ctors / functions...
};
Will initialize both x and y to 0. Note that you can use x(), y() to initialize them disregarding of their type: That's then value initialization, and usually yields a proper...
Dynamically select data frame columns using $ and a character value
...itten as
`$`(df , V1)
or indeed
`$`(df , "V1")
But...
`$`(df , paste0("V1") )
...for instance will never work, nor will anything else that must first be evaluated in the second argument. You may only pass a string which is never evaluated.
Instead use [ (or [[ if you want to extract only...
Removing leading zeroes from a field in a SQL statement
...ve the leading zeroes from a particular field, which is a simple VARCHAR(10) field. So, for example, if the field contains '00001A', the SELECT statement needs to return the data as '1A'.
...
How to split a string and assign it to variables
...ort (
"fmt"
"strings"
)
func main() {
s := strings.Split("127.0.0.1:5432", ":")
ip, port := s[0], s[1]
fmt.Println(ip, port)
}
Output:
127.0.0.1 5432
One step, for example,
package main
import (
"fmt"
"net"
)
func main() {
host, port, err := net.SplitHostPort...
SQL keys, MUL vs PRI vs UNI
...at column.
– pgoetz
Aug 7 '19 at 16:07
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