[Python-checkins] r43728 - sandbox/trunk/overload/prettyprinting.py

[guido.van.rossum]

Author: guido.van.rossum
Date: Sat Apr  8 06:13:47 2006
New Revision: 43728

Added:
   sandbox/trunk/overload/prettyprinting.py   (contents, props changed)
Log:
A really stupid prettyprinter, showing how to inherit an overloaded function.
(The solution isn't as natural as I'd like it to be, but not 100% bad.)


Added: sandbox/trunk/overload/prettyprinting.py
==============================================================================
--- (empty file)
+++ sandbox/trunk/overload/prettyprinting.py	Sat Apr  8 06:13:47 2006
@@ -0,0 +1,59 @@
+#!/usr/bin/env python2.5
+
+"""Pretty-printing Python data structures.
+
+This is a sample testcase for function overloading.
+
+"""
+
+import sys
+
+from overloading import overloaded
+
+__metaclass__ = type
+
+class PrettyPrinter:
+
+    def __init__(self, stream=None, width=80):
+        self.stream = stream if stream is not None else sys.stdout
+        self.width = width
+        self.indent = 0
+
+    def write(self, text):
+        for line in text.splitlines(True):
+            self.stream.write(line)
+            if self.indent and line.endswith("\n"):
+                self.stream.write(" "*self.indent)
+
+    @overloaded
+    def pprint(self, obj):
+        self.write(repr(obj))
+
+    @pprint.register(object, list)
+    def pprint_list(self, obj):
+        if not obj:
+            self.write("[]")
+            return
+        sep = "["
+        self.indent += 1
+        for item in obj:
+            self.write(sep)
+            self.pprint(item)
+            sep = ",\n"
+        self.indent -= 1
+        self.write("]")
+
+class HexPrettyPrinter(PrettyPrinter):
+
+    @overloaded
+    def pprint(self, obj):
+        PrettyPrinter.pprint(self, obj)
+
+    @pprint.register(object, int)
+    @pprint.register(object, long)
+    def pprint_hex(self, obj):
+        self.write(hex(obj))
+
+PrettyPrinter().pprint([1, 2, [3, 4], 5, 6])
+print
+HexPrettyPrinter().pprint([1, 2, [3, 4], 5, 6])