diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index 1a6bc1c6..ceb0d58e 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -5,6 +5,7 @@ the interesting information about completion and goto operations.
 """
 import warnings
 from itertools import chain
+import re
 
 from jedi._compatibility import next, unicode, use_metaclass
 from jedi import settings
@@ -579,7 +580,10 @@ class Definition(use_metaclass(CachedMetaClass, BaseDefinition)):
                 d = d.get_code()
             finally:
                 first_leaf.prefix = old
-        return d.replace('\n', '').replace('\r', '')
+        # Delete comments:
+        d = re.sub('#[^\n]+\n', ' ', d)
+        # Delete multi spaces/newlines
+        return re.sub('\s+', ' ', d).strip()
 
     @property
     def desc_with_module(self):
diff --git a/jedi/parser/tokenize.py b/jedi/parser/tokenize.py
index 8a0f6bc8..6765f0b0 100644
--- a/jedi/parser/tokenize.py
+++ b/jedi/parser/tokenize.py
@@ -14,8 +14,8 @@ from __future__ import absolute_import
 import string
 import re
 from io import StringIO
-from token import (tok_name, N_TOKENS, ENDMARKER, STRING, NUMBER, NAME, OP,
-                   ERRORTOKEN, NEWLINE, INDENT, DEDENT)
+from jedi.parser.token import (tok_name, N_TOKENS, ENDMARKER, STRING, NUMBER,
+                               NAME, OP, ERRORTOKEN, NEWLINE, INDENT, DEDENT)
 
 
 cookie_re = re.compile("coding[:=]\s*([-\w.]+)")
@@ -147,8 +147,11 @@ def source_tokens(source, line_offset=0):
 
 def generate_tokens(readline, line_offset=0):
     """
-    The original stdlib Python version with minor modifications.
-    Modified to not care about dedents.
+    A heavily modified Python standard library tokenizer.
+
+    Additionally to the default information, yields also the prefix of each
+    token. This idea comes from lib2to3. The prefix contains all information
+    that is irrelevant for the parser like newlines in parentheses or comments.
     """
     paren_level = 0  # count parentheses
     indents = [0]
@@ -158,6 +161,7 @@ def generate_tokens(readline, line_offset=0):
     contline = None
     new_line = False
     prefix = ''  # Should never be required, but here for safety
+    additional_prefix = ''
     while True:            # loop over lines in stream
         line = readline()  # readline returns empty when finished. See StringIO
         if not line:
@@ -192,7 +196,8 @@ def generate_tokens(readline, line_offset=0):
                 pos += 1
                 continue
 
-            prefix = pseudomatch.group(1)
+            prefix = pseudomatch.group(1) + additional_prefix
+            additional_prefix = ''
             start, pos = pseudomatch.span(2)
             spos = (lnum, start)
             token, initial = line[start:pos], line[start]
@@ -213,10 +218,12 @@ def generate_tokens(readline, line_offset=0):
             elif initial in '\r\n':
                 if not new_line and paren_level == 0:
                     yield NEWLINE, token, spos, prefix
+                else:
+                    additional_prefix = prefix + token
                 new_line = True
-            elif initial == '#':
+            elif initial == '#':  # Comments
                 assert not token.endswith("\n")
-                #yield Token(COMMENT, token, spos, prefix)
+                additional_prefix = prefix + token
             elif token in triple_quoted:
                 endprog = endprogs[token]
                 endmatch = endprog.match(line, pos)
diff --git a/jedi/parser/user_context.py b/jedi/parser/user_context.py
index b34d82a9..5562c783 100644
--- a/jedi/parser/user_context.py
+++ b/jedi/parser/user_context.py
@@ -59,7 +59,7 @@ class UserContext(object):
             first_line = (tok_str.splitlines() or [''])[0]
             column -= len(first_line)
             # Reverse the token again, so that it is in normal order again.
-            yield typ, tok_str[::-1], (self._line_temp, column), prefix
+            yield typ, tok_str[::-1], (self._line_temp, column), prefix[::-1]
 
     def _calc_path_until_cursor(self, start_pos):
         """
@@ -122,7 +122,7 @@ class UserContext(object):
                     break
 
             start_cursor = tok_start_pos
-            string = tok_str + string
+            string = tok_str + prefix + string
             last_type = tok_type
 
         # Don't need whitespace around a statement.
diff --git a/test/completion/goto.py b/test/completion/goto.py
index ad438309..18cb8502 100644
--- a/test/completion/goto.py
+++ b/test/completion/goto.py
@@ -181,13 +181,13 @@ ab1(ClassDef);ab2(ClassDef);ab3(ClassDef)
 # -----------------
 
 for i in range(1):
-    #! ['for i in range(1):    i']
+    #! ['for i in range(1): i']
     i
 
 for key, value in [(1,2)]:
-    #! ['for key, value in [(1,2)]:    key']
+    #! ['for key, value in [(1,2)]: key']
     key
 
 for i in []:
-    #! ['for i in []:    i']
+    #! ['for i in []: i']
     i