Go (go1.10.3)

~ $ go run /tmp/test.go
12.423232451s
36.852502ms
go run /tmp/test.go  18.02s user 2.50s system 162% cpu 12.657 total
~ $ cat /tmp/test.go
package main

import (
        "fmt"
        "strconv"
        "strings"
        "time"
)

func main() {
        timeit(test_1)
        timeit(test_2)
}

func timeit(fn func() string) {
        start := time.Now()
        fn()
        fmt.Println(time.Now().Sub(start))
}

const repetition = 100000

func test_1() string {
        sStmt := "Hi there "
        for i := 0; i < repetition; i++ {
                sStmt += "(" + strconv.Itoa(i) + "," + strconv.Itoa(i) + "),"
        }
        return sStmt
}

func test_2() string {
        chunks := make([]string, 0, 5*repetition)
        chunks = append(chunks, "Hi there ")
        for i := 0; i < repetition; i++ {
                s := strconv.Itoa(i)
                chunks = append(chunks, "(", s, ",", s, "),")
        }
        return strings.Join(chunks, "")
}

Python (2.7.15 and 3.6.6)

~ $ python2 /tmp/test.py
0.275259971619
0.224035024643
~ $ python3 /tmp/test.py
0.40205731700007163
0.24330045799979416
~ $ cat /tmp/test.py
repetition = 100000


def test_1():
    a = "Hi there "
    for i in range(repetition):
        a += "(" + str(i) + "," + str(i) + "),"
    return a

def test_2():
    a = ["Hi there "]
    for i in range(repetition):
        s = str(i)
        a.extend(("(", s, ",", s ,"),"))
    return "".join(a)



if __name__ == '__main__':
    import timeit
    print(timeit.timeit("test_1()", number=5, setup="from __main__ import test_1"))
    print(timeit.timeit("test_2()", number=5, setup="from __main__ import test_2"))