diff --git a/dist/pythonlibs/riotctrl_shell/gnrc.py b/dist/pythonlibs/riotctrl_shell/gnrc.py
index bb6861900a..d0c97dc63c 100644
--- a/dist/pythonlibs/riotctrl_shell/gnrc.py
+++ b/dist/pythonlibs/riotctrl_shell/gnrc.py
@@ -18,6 +18,20 @@ from riotctrl.shell import ShellInteraction, ShellInteractionParser
 # ==== Parsers ====
 
 class GNRCICMPv6EchoParser(ShellInteractionParser):
+    def __init__(self):
+        self.c_reply = re.compile(r"\d+ bytes from "
+                                  r"(?P<source>[0-9a-f:]+(%\S+)?): "
+                                  r"icmp_seq=(?P<seq>\d+) ttl=(?P<ttl>\d+)"
+                                  r"( rssi=(?P<rssi>-?\d+) dBm)?"
+                                  r"( time=(?P<rtt>\d+.\d+) ms)?"
+                                  r"(?P<dup> \(DUP\))?")
+        self.c_stats = re.compile(r"(?P<tx>\d+) packets transmitted, "
+                                  r"(?P<rx>\d+) packets received, "
+                                  r"((?P<dup>\d+) duplicates, )?"
+                                  r"(?P<packet_loss>\d+)% packet loss")
+        self.c_rtts = re.compile(r"round-trip min/avg/max = (?P<min>\d+.\d+)/"
+                                 r"(?P<avg>\d+.\d+)/(?P<max>\d+.\d+) ms")
+
     @staticmethod
     def _add_reply(res, reply):
         reply["seq"] = int(reply["seq"])
@@ -106,29 +120,18 @@ class GNRCICMPv6EchoParser(ShellInteractionParser):
         8.839
         """
         res = {}
-        c_reply = re.compile(r"\d+ bytes from (?P<source>[0-9a-f:]+(%\S+)?): "
-                             r"icmp_seq=(?P<seq>\d+) ttl=(?P<ttl>\d+)"
-                             r"( rssi=(?P<rssi>-?\d+) dBm)?"
-                             r"( time=(?P<rtt>\d+.\d+) ms)?"
-                             r"(?P<dup> \(DUP\))?")
-        c_stats = re.compile(r"(?P<tx>\d+) packets transmitted, "
-                             r"(?P<rx>\d+) packets received, "
-                             r"((?P<dup>\d+) duplicates, )?"
-                             r"(?P<packet_loss>\d+)% packet loss")
-        c_rtts = re.compile(r"round-trip min/avg/max = (?P<min>\d+.\d+)/"
-                            r"(?P<avg>\d+.\d+)/(?P<max>\d+.\d+) ms")
         for line in cmd_output.splitlines():
             if "stats" not in res:  # If final stats were not found yet
-                m = c_reply.match(line)
+                m = self.c_reply.match(line)
                 if m is not None:
                     self._add_reply(res, m.groupdict())
                     continue
-                m = c_stats.match(line)
+                m = self.c_stats.match(line)
                 if m is not None:
                     self._set_stats(res, m.groupdict())
                     continue
             else:
-                m = c_rtts.match(line)
+                m = self.c_rtts.match(line)
                 if m is not None:
                     self._set_rtts(res, m.groupdict())
         return res
@@ -164,6 +167,21 @@ class GNRCPktbufStatsResults(dict):
 
 
 class GNRCPktbufStatsParser(ShellInteractionParser):
+    def __init__(self):
+        self.c_init1 = re.compile(
+            r"packet buffer: first byte: 0x(?P<first_byte>[0-9A-Fa-f]+), "
+            r"last byte: 0x(?P<last_byte>[0-9A-Fa-f]+) "
+            r"\(size: +(?P<size>\d+)\)"
+        )
+        self.c_init2 = re.compile(r"  position of last byte used: (\d+)")
+        self.c_unused = re.compile(
+            r"~ unused: 0x(?P<start>[0-9A-Fa-f]+) "
+            # flake reports r'\(', r'\)' as invalid escape sequence
+            # false positively
+            r"\(next: ""(0x(?P<next>[0-9A-Fa-f]+)|\(nil\)), "   # noqa W605
+            r"size: +(?P<size>\d+)\) ~"
+        )
+
     @staticmethod
     def _init_res(first_byte, last_byte, size):
         return GNRCPktbufStatsResults((
@@ -220,30 +238,22 @@ class GNRCPktbufStatsParser(ShellInteractionParser):
         >>> res["first_unused"]["size"]
         8192
         """
-        c_init1 = re.compile(r"packet buffer: "
-                             r"first byte: 0x(?P<first_byte>[0-9A-Fa-f]+), "
-                             r"last byte: 0x(?P<last_byte>[0-9A-Fa-f]+) "
-                             r"\(size: +(?P<size>\d+)\)")
-        c_init2 = re.compile(r"  position of last byte used: (\d+)")
-        c_unused = re.compile(r"~ unused: 0x(?P<start>[0-9A-Fa-f]+) "
-                              r"\(next: (0x(?P<next>[0-9A-Fa-f]+)|\(nil\)), "
-                              r"size: +(?P<size>\d+)\) ~")
         res = None
         for line in cmd_output.splitlines():
             if res is None:
-                m = c_init1.match(line)
+                m = self.c_init1.match(line)
                 if m is not None:
                     res = self._init_res(**m.groupdict())
                 # no sense in further parsing if we did not find the first line
                 # yet. If we found it just continue parsing with next line
                 continue
             elif "last_byte_used" not in res:
-                m = c_init2.match(line)
+                m = self.c_init2.match(line)
                 if m is not None:
                     self._set_last_byte_used(res, m.group(1))
                     continue
             elif "first_unused" not in res:
-                m = c_unused.match(line)
+                m = self.c_unused.match(line)
                 if m is not None:
                     self._set_first_unused(res, m.groupdict())
         if res is not None and "last_byte_used" not in res: