Replace b('str') with b'str' in Python 3

This avoids an encode() call for each of these constants.

Use a custom 2to3 fixer in setup.py to perform the conversion.

1 files changed, 20 insertions, 0 deletions

diff --git a/scripts/fix_b.py b/scripts/fix_b.py
new file mode 100644
index 0000000..ccc8e1c
--- /dev/null
+++ b/scripts/fix_b.py
@@ -0,0 +1,20 @@
+"""Fixer to change b('string') into b'string'."""
+# Author: Daniele Varrazzo
+
+import token
+from lib2to3 import fixer_base
+from lib2to3.pytree import Leaf
+
+class FixB(fixer_base.BaseFix):
+
+    PATTERN = """
+              power< wrapper='b' trailer< '(' arg=[any] ')' > rest=any* >
+              """
+
+    def transform(self, node, results):
+        arg = results['arg']
+        wrapper = results["wrapper"]
+        if len(arg) == 1 and arg[0].type == token.STRING:
+            b = Leaf(token.STRING, 'b' + arg[0].value, prefix=wrapper.prefix)
+            node.children = [ b ] + results['rest']
+