Fix regex SyntaxWarnings (#610)

* Support negative-valued action parameters
by converting them in the Python helper code into a positive value
whose bit pattern is the 2's complement representation of the negative
value.

* Prevent SyntaxWarning occurrences when compiling several regex strings

Author: jafingerhut

utils/p4runtime_lib/convert.py

@@ -23,7 +23,7 @@
 - Ethernet address strings
 '''
 
-mac_pattern = re.compile('^([\da-fA-F]{2}:){5}([\da-fA-F]{2})$')
+mac_pattern = re.compile(r'^([\da-fA-F]{2}:){5}([\da-fA-F]{2})$')
 def matchesMac(mac_addr_string):
     return mac_pattern.match(mac_addr_string) is not None
 
@@ -33,7 +33,7 @@ def encodeMac(mac_addr_string):
 def decodeMac(encoded_mac_addr):
     return ':'.join(s.hex() for s in encoded_mac_addr)
 
-ip_pattern = re.compile('^(\d{1,3}\.){3}(\d{1,3})$')
+ip_pattern = re.compile(r'^(\d{1,3}\.){3}(\d{1,3})$')
 def matchesIPv4(ip_addr_string):
     return ip_pattern.match(ip_addr_string) is not None
 

utils/p4runtime_lib/helper.py

@@ -59,14 +59,14 @@ def get_alias(self, entity_type, id):
     def __getattr__(self, attr):
         # Synthesize convenience functions for name to id lookups for top-level entities
         # e.g. get_tables_id(name_string) or get_actions_id(name_string)
-        m = re.search("^get_(\w+)_id$", attr)
+        m = re.search(r"^get_(\w+)_id$", attr)
         if m:
             primitive = m.group(1)
             return lambda name: self.get_id(primitive, name)
 
         # Synthesize convenience functions for id to name lookups
         # e.g. get_tables_name(id) or get_actions_name(id)
-        m = re.search("^get_(\w+)_name$", attr)
+        m = re.search(r"^get_(\w+)_name$", attr)
         if m:
             primitive = m.group(1)
             return lambda id: self.get_name(primitive, id)