正则表达式中匹配没有小写和至少一个大写？

Question

I need to find a regex in go that match when there is no lowercase and at least one uppercase.

For example:

"1 2 3 A"  : Match
"1 2 3"    : No match
"a A "     : no match
"AHKHGJHB" : Match

This work but in PHP not in Go (the ?= token isn't working in Go):

(?=.*[A-Z].*)(?=^[^a-z]*$)

In my code this line call the regex:

isUppcase, _ := reg.MatchString(`^[^a-z]*$`, string)

Actually my regex catch when there is no lowercase but I want it also to catch when there is at least one uppercase.

Answer 1

You may use

^\P{Ll}*\p{Lu}\P{Ll}*$

Or, a bit more efficient:

^\P{L}*\p{Lu}\P{Ll}*$

See the regex demo.

Details

• ^ - start of string
• ^\P{L}* - 0 or more chars other than letters
• \p{Lu} - an uppercase letter
• \P{Ll}* - 0 or more chars other than lowercase letters
• $ - end of string.

Go test:

package main

import (
    "regexp"
    "fmt"
)

func main() {
    re := regexp.MustCompile(`^\P{L}*\p{Lu}\P{Ll}*$`)
    fmt.Println(re.MatchString(`1 2 3 A`))   
    fmt.Println(re.MatchString(`1 2 3`))   
    fmt.Println(re.MatchString(`a A`))   
    fmt.Println(re.MatchString(`AHKHGJHB`))   
    fmt.Println(re.MatchString(`Δ != Γ`)) 
}

Output:

true
false
false
true
true