I have a string as just MyString and I want to append in this data something like this:
MYString ("1", "a"), ("1", "b") //END result
My code is something like this:
query := "MyString";
array := []string{"a", "b"}
for i , v := range array{
id := "1"
fmt.Println(v,i)
query += '("{}", "{}"), '.format(id, v)
}
but I am getting two errors:
./prog.go:15:23: more than one character in rune literal
./prog.go:15:39: '\u0000'.format undefined (type rune has no field or method format)
You can't use single quotes for Strings in Go. You can only use double-quotes or backticks.
Single quotes are used for single characters, called runes
Change your line to:
query += "(\"{}\", \"{}\"), ".format(id, v)
or
query += `("{}", "{}"), `.format(id, v)
However, Go is not python. Go doesn't have a format method like that. But it has fmt.Sprintf.
So to really fix it, use:
query = fmt.Sprintf(`%s("%s", "%s"), `, query, id, v)
Issue here is single quotes . Go Compiler expects a character only when encounters '' . Rather use double quotes with escape symbol as explained in above example.
Related
a := []byte("H") //works
a := []byte{"H"} //does not compile
What is the conceptual difference between () and {} as used above?
The reason is the difference between type conversions and slice literals.
_ = []byte("Hi!") // Converts a string literal to a []byte.
_ = []byte{'H', 'i', '!'} // Initializes a []byte literal
Your second example []byte{"H"} fails to compile because "H" is a string literal that is being used in place of a rune literal, it's comparable to trying to assign a string to a byte typed variable:
var y byte = 'H' // OK
var x byte = "H" // ERROR: cannot use "H" (type string) as type byte in assignment
In the first one a := []byte("H") you are type casting the string "H" into a byte array.
In the second one a := []byte{"H"} you are defining a byte array and assigning "H" as it's first value, which is invalid.
You can compare the second one with defining a string array:
s := []string{"hello","world",".."} // works
f := []string{1,2,4} // fails because the datatype is wrong
I have a string in Golang called mystring and I want to put it between 2 percentage signs (like this %mystring%). However until now I wasn't able to do it.
The things that I have tried are:
value := fmt.Sprintf("%%s%",mystring)
value := fmt.Sprintf("%s%s%s","%",mystring,"%")
value := fmt.Sprintf("/% %s/%",mystring)
But when I print it, in the end I receive a nil. Example: the value of mystring is "HelloWorld" then I get: %HelloWorld%nil
Right now I am receiving this as result:
/%s/%!(NOVERB)%!(EXTRA string=HelloWorld)<nil>
So, what am I missing?
Thanks.
You need to escape the %'s in format string using another %:
value := fmt.Sprintf("%%%s%%",mystring)
Use %% in your format string for an actual %.
For example:
func main() {
mystring := "hello"
value := fmt.Sprintf("%%%s%%", mystring)
fmt.Println(value)
}
Prints: %hello%
This is clearly documented at the beginning of the docs for fmt:
%% a literal percent sign; consumes no value
I try to generate a sql query using Sprintf() where I have to use the same variable two times
myStr := "test"
str := Sprintf("SELECT ... WHERE a = '%#[1]s' or b = '%#[1]s'", myStr)
fmt.Println(str)
This snippets outputs the expected string
SELECT ... WHERE a = 'test' or b = 'test'
but go vet says:
unrecognized printf flag for verb 's': '#' (vet)
And I am puzzled why. Switching the printf verb to v satisfies go vet but adds " around my string. And I honestly doesn't see a mistake in using %#[1]s.
Any thoughts?
Using printf to construct queries is a bad idea, it opens you up to SQL injection.
See named parameters in the sql package.
There is no # Sprintf flag for a string verb (the flag # is e.g. adding 0x for hex values: %#x). So remove it to make your go vet troubles disappear:
myStr := "test"
str := Sprintf("SELECT ... WHERE a = '%[1]s' or b = '%[1]s'", myStr)
fmt.Println(str)
But: If any part of your constructed query (myStr) comes from external input (i.e. user input), you really should follow Hein's advise and use named parameters.
I am building a small tool which parses a user's input and finds common pitfalls in writing and flags them so the user can improve their text. So far everything works well except for text that has curly quotes compared to normal ASCII straight quotes. I have a hack now which will do a string replacement for opening (and closing) single curly quotes and double opening (and close) curly quotes like so:
cleanedData := bytes.Replace([]byte(data), []byte("’"), []byte("'"), -1)
I feel like there must be a better way to handle this in the stdlib so I can also convert other non-ascii characters to an ascii equivalent. Any help would be greatly appreciated.
The strings.Map function looks to me like what you want.
I don't know of a generic 'ToAscii' type function, but Map has a nice approach for mapping runes to other runes.
Example (updated):
func main() {
data := "Hello “Frank” or ‹François› as you like to be ‘called’"
fmt.Printf("Original: %s\n", data)
cleanedData := strings.Map(normalize, data)
fmt.Printf("Cleaned: %s\n", cleanedData)
}
func normalize(in rune) rune {
switch in {
case '“', '‹', '”', '›':
return '"'
case '‘', '’':
return '\''
}
return in
}
Output:
Original: Hello “Frank” or ‹François› as you like to be ‘called’
Cleaned: Hello "Frank" or "François" as you like to be 'called'
I'm trying to do the rather simple task of splitting a string by newlines.
This does not work:
temp := strings.Split(result,`\n`)
I also tried ' instead of ` but no luck.
Any ideas?
You have to use "\n".
Splitting on `\n`, searches for an actual \ followed by n in the text, not the newline byte.
playground
For those of us that at times use Windows platform, it can
help remember to use replace before split:
strings.Split(strings.ReplaceAll(windows, "\r\n", "\n"), "\n")
Go Playground
It does not work because you're using backticks:
Raw string literals are character sequences between back quotes ``. Within the quotes, any character is legal except back quote. The value of a raw string literal is the string composed of the uninterpreted (implicitly UTF-8-encoded) characters between the quotes; in particular, backslashes have no special meaning and the string may contain newlines.
Reference: http://golang.org/ref/spec#String_literals
So, when you're doing
strings.Split(result,`\n`)
you're actually splitting using the two consecutive characters "\" and "n", and not the character of line return "\n". To do what you want, simply use "\n" instead of backticks.
Your code doesn't work because you're using backticks instead of double quotes. However, you should be using a bufio.Scanner if you want to support Windows.
import (
"bufio"
"strings"
)
func SplitLines(s string) []string {
var lines []string
sc := bufio.NewScanner(strings.NewReader(s))
for sc.Scan() {
lines = append(lines, sc.Text())
}
return lines
}
Alternatively, you can use strings.FieldsFunc (this approach skips blank lines)
strings.FieldsFunc(s, func(c rune) bool { return c == '\n' || c == '\r' })
import regexp
var lines []string = regexp.MustCompile("\r?\n").Split(inputString, -1)
MustCompile() creates a regular expression that allows to split by both \r\n and \n
Split() performs the split, seconds argument sets maximum number of parts, -1 for unlimited
' doesn't work because it is not a string type, but instead a rune.
temp := strings.Split(result,'\n')
go compiler: cannot use '\u000a' (type rune) as type string in argument to strings.Split
definition: Split(s, sep string) []string