From 355e7ddbcf963816e6d2c1eda2bf0cb961b79fa0 2011-11-20 16:11:58
From: Thomas Kluyver <takowl@gmail.com>
Date: 2011-11-20 16:11:58
Subject: [PATCH] Copy EvalFormatter and FullEvalFormatter from prompt-manager branch.

---

diff --git a/IPython/utils/text.py b/IPython/utils/text.py
index cfec757..01d3d8d 100644
--- a/IPython/utils/text.py
+++ b/IPython/utils/text.py
@@ -597,33 +597,52 @@ def wrap_paragraphs(text, ncols=80):
     return out_ps
 
 
-
 class EvalFormatter(Formatter):
     """A String Formatter that allows evaluation of simple expressions.
-
-    Any time a format key is not found in the kwargs,
-    it will be tried as an expression in the kwargs namespace.
-
+    
+    Note that this version interprets a : as specifying a format string (as per
+    standard string formatting), so if slicing is required, you must explicitly
+    create a slice.
+    
     This is to be used in templating cases, such as the parallel batch
     script templates, where simple arithmetic on arguments is useful.
 
     Examples
     --------
+    
+    In  [1]: f = EvalFormatter()
+    In  [2]: f.format('{n//4}', n=8)
+    Out [2]: '2'
+    
+    In  [3]: f.format("{greeting[slice(2,4)]}", greeting="Hello")
+    Out [3]: 'll'
+    """
+    def get_field(self, name, args, kwargs):
+        v = eval(name, kwargs)
+        return v, name
 
-    In [1]: f = EvalFormatter()
+class FullEvalFormatter(Formatter):
+    """A String Formatter that allows evaluation of simple expressions.
+    
+    Any time a format key is not found in the kwargs,
+    it will be tried as an expression in the kwargs namespace.
+    
+    Note that this version allows slicing using [1:2], so you cannot specify
+    a format string. Use :class:`EvalFormatter` to permit format strings.
+    
+    Examples
+    --------
+    
+    In [1]: f = FullEvalFormatter()
     In [2]: f.format('{n//4}', n=8)
     Out[2]: '2'
-
-    In [3]: f.format('{list(range(3))}')
-    Out[3]: '[0, 1, 2]'
+    
+    In [3]: f.format('{list(range(5))[2:4]}')
+    Out[3]: '[2, 3]'
 
     In [4]: f.format('{3*2}')
     Out[4]: '6'
     """
-
-    # should we allow slicing by disabling the format_spec feature?
-    allow_slicing = True
-
     # copied from Formatter._vformat with minor changes to allow eval
     # and replace the format_spec code with slicing
     def _vformat(self, format_string, args, kwargs, used_args, recursion_depth):
@@ -640,12 +659,11 @@ class EvalFormatter(Formatter):
             # if there's a field, output it
             if field_name is not None:
                 # this is some markup, find the object and do
-                #  the formatting
+                # the formatting
 
-                if self.allow_slicing and format_spec:
+                if format_spec:
                     # override format spec, to allow slicing:
                     field_name = ':'.join([field_name, format_spec])
-                    format_spec = ''
 
                 # eval the contents of the field for the object
                 # to be formatted
@@ -654,12 +672,8 @@ class EvalFormatter(Formatter):
                 # do any conversion on the resulting object
                 obj = self.convert_field(obj, conversion)
 
-                # expand the format spec, if needed
-                format_spec = self._vformat(format_spec, args, kwargs,
-                                            used_args, recursion_depth-1)
-
                 # format the object and append to the result
-                result.append(self.format_field(obj, format_spec))
+                result.append(self.format_field(obj, ''))
 
         return ''.join(result)