Add a prefix splitting.

parso/python/prefix.py

@@ -0,0 +1,50 @@
+import re
+
+from parso.tokenize import group
+
+
+class PrefixToken(object):
+    def __init__(self, value, start_pos):
+        self.value = value
+        self.start_pos = start_pos
+
+    @property
+    def end_pos(self):
+        if '\n' in self.value:
+            return self.start_pos[0] + 1, 0
+        return self.end_pos[1]
+
+
+_comment = r'#[^\n\r\f]*'
+_backslash = r'\\\r?\n?'
+_whitespace = r' +'
+_newline = r'\r?\n'
+_form_feed = r'\f'
+
+_regex = group(_comment, _backslash, _whitespace, _newline, _form_feed)
+_regex = re.compile(_regex)
+
+
+_types = {
+    ' ': 'spaces',
+    '#': 'comment',
+    '\\': 'backslash',
+    '\f': 'form_feed',
+    '\n': 'newline',
+    '\r': 'newline'
+}
+
+
+def split_prefix(prefix, start_pos):
+    line, column = start_pos
+    start = 0
+    while start != len(prefix):
+        match =_regex.match(prefix, start)
+        value = match.group(0)
+        yield PrefixToken(value, (line, column + start))
+
+        start = match.end(0)
+        print(start)
+        if '\n' in value:
+            line += 1
+            column = -start