changeset:   100942:f04ddbc47005
tag:         tip
user:        Victor Stinner <victor.stinner@gmail.com>
date:        Tue Apr 12 18:23:59 2016 +0200
files:       Lib/modulefinder.py
description:
Issue #26647: Optimize ModuleFinder.scan_opcodes_25()

Use an index rather than creating a lot of substrings.


diff -r 423e2a96189e -r f04ddbc47005 Lib/modulefinder.py
--- a/Lib/modulefinder.py	Tue Apr 12 18:17:06 2016 +0200
+++ b/Lib/modulefinder.py	Tue Apr 12 18:23:59 2016 +0200
@@ -338,33 +338,35 @@ class ModuleFinder:
                         self._add_badmodule(fullname, caller)
 
     def scan_opcodes_25(self, co,
-                     unpack = struct.unpack):
+                        unpack=struct.unpack):
         # Scan the code, and yield 'interesting' opcode combinations
         # Python 2.5 version (has absolute and relative imports)
         code = co.co_code
+        index = 0
         names = co.co_names
         consts = co.co_consts
         LOAD_LOAD_AND_IMPORT = LOAD_CONST + LOAD_CONST + IMPORT_NAME
-        while code:
-            c = bytes([code[0]])
+        while index < len(code):
+            c = bytes([code[index]])
             if c in STORE_OPS:
-                oparg, = unpack('<H', code[1:3])
+                oparg, = unpack('<H', code[index+1:index+3])
                 yield "store", (names[oparg],)
-                code = code[3:]
+                index += 3
                 continue
-            if code[:9:3] == LOAD_LOAD_AND_IMPORT:
-                oparg_1, oparg_2, oparg_3 = unpack('<xHxHxH', code[:9])
+            if code[index:index+9:3] == LOAD_LOAD_AND_IMPORT:
+                oparg_1, oparg_2, oparg_3 = unpack('<xHxHxH',
+                                                   code[index:index+9])
                 level = consts[oparg_1]
                 if level == 0: # absolute import
                     yield "absolute_import", (consts[oparg_2], names[oparg_3])
                 else: # relative import
                     yield "relative_import", (level, consts[oparg_2], names[oparg_3])
-                code = code[9:]
+                index += 9
                 continue
             if c >= HAVE_ARGUMENT:
-                code = code[3:]
+                index += 3
             else:
-                code = code[1:]
+                index += 1
 
     def scan_code(self, co, m):
         code = co.co_code