Python stdlib is now not measured by default. If needed, turn it on with the -L switch.

Author: nedbat

CHANGES.txt

@@ -10,6 +10,9 @@ HTML reporting, and continued refactoring.
 - HTML reports and annotation of source files: use the new -b switch.  Thanks
   to George Song for code, inspiration and guidance.
 
+- Code in the Python standard library is not measured by default.  If you need
+  to measure standard library code, use the -L switch during execution.
+
 - Annotation into a directory (-a -d) behaves differently.  The annotated files
   are named with their hierarchy flattened so that same-named files from
   different directories no longer collide.  Also, only files in the current

coverage/cmdline.py

@@ -9,10 +9,11 @@
 
 Usage:
 
-coverage -x [-p] MODULE.py [ARG1 ARG2 ...]
+coverage -x [-p] [-L] MODULE.py [ARG1 ARG2 ...]
     Execute the module, passing the given command-line arguments, collecting
     coverage data.  With the -p option, include the machine name and process
-    ID in the .coverage file name.
+    ID in the .coverage file name.  With -L, measure coverage even inside the
+    Python standard library, which isn't done by default.
 
 coverage -e
     Erase collected coverage data.
@@ -86,6 +87,7 @@ def command_line(self, argv, help_fn=None):
             '-e': 'erase',
             '-h': 'help',
             '-i': 'ignore-errors',
+            '-L': 'stdlib',
             '-m': 'show-missing',
             '-p': 'parallel-mode',
             '-r': 'report',
@@ -135,6 +137,7 @@ def command_line(self, argv, help_fn=None):
 
         # Do something.
         self.coverage.parallel_mode = settings.get('parallel-mode')
+        self.coverage.cover_stdlib = settings.get('stdlib')
         self.coverage.get_ready()
 
         if settings.get('erase'):

coverage/control.py

@@ -1,6 +1,6 @@
 """Core control stuff for coverage.py"""
 
-import os, socket
+import os, socket, sys
 
 from coverage.annotate import AnnotateReporter
 from coverage.codeunit import code_unit_factory
@@ -17,11 +17,13 @@ def __init__(self):
 
         self.parallel_mode = False
         self.exclude_re = ''
+        self.cover_stdlib = False
         self.nesting = 0
+        
         self.file_locator = FileLocator()
+        self.sysprefix = self.file_locator.abs_file(sys.prefix)
 
         self.collector = Collector(self.should_trace)
-        
         self.data = CoverageData(collector="coverage.py v%s" % __version__)
 
         # The default exclude pattern.
@@ -36,14 +38,20 @@ def should_trace(self, filename):
         
         Returns a canonicalized filename if it should be traced, False if it
         should not.
+        
         """
         if filename == '<string>':
             # There's no point in ever tracing string executions, we can't do
             # anything with the data later anyway.
             return False
-        # TODO: flag: ignore std lib?
+        
+        canonical = self.file_locator.canonical_filename(filename)
+        if not self.cover_stdlib:
+            if canonical.startswith(self.sysprefix):
+                return False
+        
         # TODO: ignore by module as well as file?
-        return self.file_locator.canonical_filename(filename)
+        return canonical
 
     def use_cache(self, usecache):
         """Control the use of a data file (incorrectly called a cache).

test/test_coverage.py

@@ -1688,6 +1688,44 @@ def testFileNames(self):
         filename, _, _, _ = cov.analysis(sys.modules["mymod"])
         self.assertEqual(os.path.basename(filename), "mymod.py")
 
+    def testIgnoreStdLib(self):
+        self.makeFile("mymain", """\
+            import mymod, colorsys
+            a = 1
+            hls = colorsys.rgb_to_hls(1.0, 0.5, 0.0)
+            """)
+            
+        self.makeFile("mymod", """\
+            fooey = 17
+            """)
+
+        # Measure without the stdlib.
+        cov1 = coverage.coverage()
+        self.assertEqual(cov1.cover_stdlib, False)
+        cov1.start()
+        self.importModule("mymain")
+        cov1.stop()
+
+        # some statements were marked executed in mymain.py
+        _, statements, missing, _ = cov1.analysis("mymain.py")
+        self.assertNotEqual(statements, missing)
+        # but none were in colorsys.py
+        _, statements, missing, _ = cov1.analysis("colorsys.py")
+        self.assertEqual(statements, missing)
+
+        # Measure with the stdlib.
+        cov2 = coverage.coverage()
+        cov2.cover_stdlib = True
+        cov2.start()
+        self.importModule("mymain")
+        cov2.stop()
+
+        # some statements were marked executed in mymain.py
+        _, statements, missing, _ = cov2.analysis("mymain.py")
+        self.assertNotEqual(statements, missing)
+        # and some were marked executed in colorsys.py
+        _, statements, missing, _ = cov2.analysis("colorsys.py")
+        self.assertNotEqual(statements, missing)
 
 
 class ProcessTest(CoverageTest):