PlayerPrefs.SetFloat("Player Score", 10.0);

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        PlayerPrefs.SetFloat("Player Score", 10.0F);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        PlayerPrefs.SetFloat('Player Score', 10.0F)