Issue #27078: Added BUILD_STRING opcode.  Optimized f-strings evaluation.
diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index 46f1bab..d36e4ac 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -232,7 +232,8 @@
 #     Python 3.6a1  3370 (16 bit wordcode)
 #     Python 3.6a1  3371 (add BUILD_CONST_KEY_MAP opcode #27140)
 #     Python 3.6a1  3372 (MAKE_FUNCTION simplification, remove MAKE_CLOSURE
-                          #27095)
+#                         #27095)
+#     Python 3.6b1  3373 (add BUILD_STRING opcode #27078)
 #
 # MAGIC must change whenever the bytecode emitted by the compiler may no
 # longer be understood by older implementations of the eval loop (usually
@@ -241,7 +242,7 @@
 # Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
 # in PC/launcher.c must also be updated.
 
-MAGIC_NUMBER = (3372).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3373).to_bytes(2, 'little') + b'\r\n'
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 
 _PYCACHE = '__pycache__'
diff --git a/Lib/opcode.py b/Lib/opcode.py
index 0640819..d9202e8 100644
--- a/Lib/opcode.py
+++ b/Lib/opcode.py
@@ -213,5 +213,6 @@
 
 def_op('FORMAT_VALUE', 155)
 def_op('BUILD_CONST_KEY_MAP', 156)
+def_op('BUILD_STRING', 157)
 
 del def_op, name_op, jrel_op, jabs_op