Avoid unnecessary calculation of indent on every line

IPython/core/inputsplitter.py

@@ -290,10 +290,11 b' class InputSplitter(object):'
             isp.push(line)
         print 'Input source was:\n', isp.source_reset(),
     """
-    # Number of spaces of indentation computed from input that has been pushed
-    # so far.  This is the attributes callers should query to get the current
-    # indentation level, in order to provide auto-indent facilities.
-    indent_spaces = 0
+    # A cache for calculating the current indentation.
+    # If the first value matches self.source, the second value is an integer
+    # number of spaces for the current indentation. If the first value does not
+    # match, self.source has changed, and the indentation must be recalculated.
+    _indent_spaces_cache = None, None
     # String, indicating the default input encoding.  It is computed by default
     # at initialization time via get_input_encoding(), but it can be reset by a
     # client with specific knowledge of the encoding.
@@ -327,7 +328,6 b' class InputSplitter(object):'
 
     def reset(self):
         """Reset the input buffer and associated state."""
-        self.indent_spaces = 0
         self._buffer[:] = []
         self.source = ''
         self.code = None
@@ -371,7 +371,7 b' class InputSplitter(object):'
             if self._is_invalid:
                 return 'invalid', None
             elif self.push_accepts_more():
-                return 'incomplete', self.indent_spaces
+                return 'incomplete', self.get_indent_spaces()
             else:
                 return 'complete', None
         finally:
@@ -412,7 +412,6 b' class InputSplitter(object):'
         if source.endswith('\\\n'):
             return False
 
-        self._update_indent()
         try:
             with warnings.catch_warnings():
                 warnings.simplefilter('error', SyntaxWarning)
@@ -470,7 +469,7 b' class InputSplitter(object):'
         # If there's just a single line or AST node, and we're flush left, as is
         # the case after a simple statement such as 'a=1', we want to execute it
         # straight away.
-        if self.indent_spaces==0:
+        if self.get_indent_spaces() == 0:
             if len(self.source.splitlines()) <= 1:
                 return False
             
@@ -488,9 +487,15 b' class InputSplitter(object):'
         # General fallback - accept more code
         return True
 
-    def _update_indent(self):
+    def get_indent_spaces(self):
+        sourcefor, n = self._indent_spaces_cache
+        if sourcefor == self.source:
+            return n
+
         # self.source always has a trailing newline
-        self.indent_spaces = find_next_indent(self.source[:-1])
+        n = find_next_indent(self.source[:-1])
+        self._indent_spaces_cache = (self.source, n)
+        return n
 
     def _store(self, lines, buffer=None, store='source'):
         """Store one or more lines of input.

IPython/core/interactiveshell.py

@@ -1940,7 +1940,7 b' class InteractiveShell(SingletonConfigurable):'
 
     def _indent_current_str(self):
         """return the current level of indentation as a string"""
-        return self.input_splitter.indent_spaces * ' '
+        return self.input_splitter.get_indent_spaces() * ' '
 
     #-------------------------------------------------------------------------
     # Things related to text completion

IPython/core/tests/test_inputsplitter.py

@@ -37,7 +37,7 b' def mini_interactive_loop(input_func):'
     # input indefinitely, until some exit/quit command was issued.  Here we
     # only illustrate the basic inner loop.
     while isp.push_accepts_more():
-        indent = ' '*isp.indent_spaces
+        indent = ' '*isp.get_indent_spaces()
         prompt = '>>> ' + indent
         line = indent + input_func(prompt)
         isp.push(line)
@@ -132,7 +132,7 b' class InputSplitterTestCase(unittest.TestCase):'
         isp.push('x=1')
         isp.reset()
         self.assertEqual(isp._buffer, [])
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         self.assertEqual(isp.source, '')
         self.assertEqual(isp.code, None)
         self.assertEqual(isp._is_complete, False)
@@ -149,21 +149,21 b' class InputSplitterTestCase(unittest.TestCase):'
     def test_indent(self):
         isp = self.isp # shorthand
         isp.push('x=1')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\n    x=1')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('y=2\n')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
 
     def test_indent2(self):
         isp = self.isp
         isp.push('if 1:')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('    x=1')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         # Blank lines shouldn't change the indent level
         isp.push(' '*2)
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
 
     def test_indent3(self):
         isp = self.isp
@@ -171,75 +171,75 b' class InputSplitterTestCase(unittest.TestCase):'
         # shouldn't get confused.
         isp.push("if 1:")
         isp.push("    x = (1+\n    2)")
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
 
     def test_indent4(self):
         isp = self.isp
         # whitespace after ':' should not screw up indent level
         isp.push('if 1: \n    x=1')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('y=2\n')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\t\n    x=1')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('y=2\n')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
 
     def test_dedent_pass(self):
         isp = self.isp # shorthand
         # should NOT cause dedent
         isp.push('if 1:\n    passes = 5')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('if 1:\n     pass')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\n     pass   ')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
 
     def test_dedent_break(self):
         isp = self.isp # shorthand
         # should NOT cause dedent
         isp.push('while 1:\n    breaks = 5')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('while 1:\n     break')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('while 1:\n     break   ')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
 
     def test_dedent_continue(self):
         isp = self.isp # shorthand
         # should NOT cause dedent
         isp.push('while 1:\n    continues = 5')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('while 1:\n     continue')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('while 1:\n     continue   ')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
 
     def test_dedent_raise(self):
         isp = self.isp # shorthand
         # should NOT cause dedent
         isp.push('if 1:\n    raised = 4')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('if 1:\n     raise TypeError()')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\n     raise')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\n     raise      ')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
 
     def test_dedent_return(self):
         isp = self.isp # shorthand
         # should NOT cause dedent
         isp.push('if 1:\n    returning = 4')
-        self.assertEqual(isp.indent_spaces, 4)
+        self.assertEqual(isp.get_indent_spaces(), 4)
         isp.push('if 1:\n     return 5 + 493')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\n     return')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\n     return      ')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
         isp.push('if 1:\n     return(0)')
-        self.assertEqual(isp.indent_spaces, 0)
+        self.assertEqual(isp.get_indent_spaces(), 0)
 
     def test_push(self):
         isp = self.isp
@@ -508,7 +508,7 b" if __name__ == '__main__':"
         while True:
             prompt = start_prompt
             while isp.push_accepts_more():
-                indent = ' '*isp.indent_spaces
+                indent = ' '*isp.get_indent_spaces()
                 if autoindent:
                     line = indent + input(prompt+indent)
                 else: