fix(matrix, util): increase modifier random string length and optimiz…

…e random string generation

frads/matrix.py

@@ -730,7 +730,7 @@ def rfluxmtx_markup(
         Marked up primitives as strings (to be written to a file for rfluxmtx)
     """
     modifier_set = {p.modifier for p in surfaces}
-    source_modifier = f"rflx{surfaces[0].modifier}{random_string(5)}"
+    source_modifier = f"rflx{surfaces[0].modifier}{random_string(10)}"
     if left_hand:
         basis = "-" + basis
     if source not in ("glow", "light"):

frads/utils.py

@@ -6,7 +6,7 @@
 import logging
 import re
 from pathlib import Path
-from random import choice
+from random import choices
 import string
 import subprocess as sp
 from typing import Any, Dict, Optional, List, Union
@@ -529,7 +529,7 @@ def batch_process(
 def random_string(size: int) -> str:
     """Generate random characters."""
     chars = string.ascii_uppercase + string.digits
-    return "".join(choice(chars) for _ in range(size))
+    return "".join(choices(chars, k=size))
 
 
 def minutes_to_datetime(year: int, minutes: int):