Address XXX comment in dis.py: inspect.py now attempts to reuse the dis.py compiler flag values before resorting to defining its own

Lib/dis.py

@@ -68,9 +68,10 @@ def distb(tb=None):
         while tb.tb_next: tb = tb.tb_next
     disassemble(tb.tb_frame.f_code, tb.tb_lasti)
 
-# XXX This duplicates information from code.h, also duplicated in inspect.py.
-# XXX Maybe this ought to be put in a central location, like opcode.py?
-flag2name = {
+# The inspect module interrogates this dictionary to build its
+# list of CO_* constants. It is also used by pretty_flags to
+# turn the co_flags field into a human readable list.
+COMPILER_FLAG_NAMES = {
      1: "OPTIMIZED",
      2: "NEWLOCALS",
      4: "VARARGS",
@@ -86,7 +87,7 @@ def pretty_flags(flags):
     for i in range(32):
         flag = 1<<i
         if flags & flag:
-            names.append(flag2name.get(flag, hex(flag)))
+            names.append(COMPILER_FLAG_NAMES.get(flag, hex(flag)))
             flags ^= flag
             if not flags:
                 break

Lib/inspect.py

@@ -36,15 +36,25 @@ import types
 import itertools
 import string
 import re
-import dis
 import imp
 import tokenize
 import linecache
 from operator import attrgetter
 from collections import namedtuple
-# These constants are from Include/code.h.
-CO_OPTIMIZED, CO_NEWLOCALS, CO_VARARGS, CO_VARKEYWORDS = 0x1, 0x2, 0x4, 0x8
+
+# Create constants for the compiler flags in Include/code.h
+# We try to get them from dis to avoid duplication, but fall
+# back to hardcording so the dependency is optional
+try:
+    from dis import COMPILER_FLAG_NAMES as _flag_names
+except ImportError:
+    CO_OPTIMIZED, CO_NEWLOCALS = 0x1, 0x2
+    CO_VARARGS, CO_VARKEYWORDS = 0x4, 0x8
     CO_NESTED, CO_GENERATOR, CO_NOFREE = 0x10, 0x20, 0x40
+else:
+    mod_dict = globals()
+    for k, v in _flag_names.items():
+        mod_dict["CO_" + v] = k
 
 # See Include/object.h
 TPFLAGS_IS_ABSTRACT = 1 << 20

Misc/NEWS

@@ -90,6 +90,9 @@ Extensions
 Library
 -------
 
+- Address XXX comment in dis.py by having inspect.py prefer to reuse the
+  dis.py compiler flag values over defining its own
+
 - Issue #9147: Added dis.code_info() which is similar to show_code()
   but returns formatted code information in a string rather than
   displaying on screen.