Add docstring to create_template() function and make it faster (#90)

* Update create_template with documentation and change the function to use list comprehension to make it faster

* Add unit tests for the create_template function

* Add slightly faster improvement as local variable is faster than instance varable access

* Update docstring and move length assertion to top of function.

removed the param_str variable as it acts like a penalty to function executions where the param_str is not accessed at all.

Signed-off-by: Nikolai Kummer <nikolai.kummer@gmail.com>

---------

Signed-off-by: Nikolai Kummer <nikolai.kummer@gmail.com>
Co-authored-by: Superskyyy <Superskyyy@outlook.com>

drain3/drain.py

@@ -413,14 +413,16 @@ def get_seq_distance(self, seq1: Sequence[str], seq2: Sequence[str], include_par
         return ret_val, param_count
 
     def create_template(self, seq1: Sequence[str], seq2: Sequence[str]) -> Sequence[str]:
+        """
+        Loop through two sequences and create a template sequence that
+        replaces unmatched tokens with the parameter string.
+        
+        :param seq1: first sequence
+        :param seq2: second sequence
+        :return: template sequence with param_str in place of unmatched tokens
+        """
         assert len(seq1) == len(seq2)
-        ret_val = list(seq2)
-
-        for i, (token1, token2) in enumerate(zip(seq1, seq2)):
-            if token1 != token2:
-                ret_val[i] = self.param_str
-
-        return ret_val
+        return [token2 if token1 == token2 else self.param_str for token1, token2 in zip(seq1, seq2)]
 
     def match(self, content: str, full_search_strategy: str = "never") -> Optional[LogCluster]:
         """

tests/test_drain.py

@@ -257,3 +257,18 @@ def test_match_only(self):
         c: LogCluster = model.match("nothing")
         self.assertIsNone(c)
 
+    def test_create_template(self):
+        model = Drain(param_str="*")
+
+        seq1 = ["aa", "bb", "dd"]
+        seq2 = ["aa", "bb", "cc"]
+
+        # test for proper functionality
+        template = model.create_template(seq1, seq2)
+        self.assertListEqual(["aa", "bb", "*"], template)
+
+        template = model.create_template(seq1, seq1)
+        self.assertListEqual(seq1, template)
+
+        # Test for equal lengths input vectors
+        self.assertRaises(AssertionError, model.create_template, seq1, ["aa"])