Add a mill progress indicator to progress.py

I've created a progress indicator that outputs a "mill" and added it to
the `progress.py` file.

Very simple stuff but its more compact than the other progress bars and
it can be useful when using long labels.

AUTHORS

@@ -18,3 +18,4 @@ Patches and Suggestions
 - Miguel Araujo <maraujop>
 - takluyver
 - kracekumar 
+- Alejandro Gómez <alejandrogomez>

clint/textui/progress.py

@@ -15,10 +15,12 @@ import sys
 STREAM = sys.stderr
 
 BAR_TEMPLATE = '%s[%s%s] %i/%i\r'
+MILL_TEMPLATE = '%s %s %i/%i\r'  
 
 DOTS_CHAR = '.'
 BAR_FILLED_CHAR = '#'
 BAR_EMPTY_CHAR = ' '
+MILL_CHARS = ['|', '/', '-', '\\']
 
 def bar(it, label='', width=32, hide=False, empty_char=BAR_EMPTY_CHAR, filled_char=BAR_FILLED_CHAR):
     """Progress iterator. Wrap your iterables with it."""
@@ -65,3 +67,32 @@ def dots(it, label='', hide=False):
     STREAM.write('\n')
     STREAM.flush()
 
+
+def mill(it, label='', hide=False,): 
+    """Progress iterator. Prints a mill while iterating over the items."""
+
+    def _mill_char(_i):
+        if _i == 100:
+            return ' '
+        else:
+            return MILL_CHARS[_i % len(MILL_CHARS)]
+
+    def _show(_i):
+        if not hide:
+            STREAM.write(MILL_TEMPLATE % (
+                label, _mill_char(_i), _i, count))
+            STREAM.flush()
+
+    count = len(it)
+
+    if count:
+        _show(0)
+
+    for i, item in enumerate(it):
+
+        yield item
+        _show(i+1)
+
+    if not hide:
+        STREAM.write('\n')
+        STREAM.flush()

examples/progressbar.py

@@ -17,4 +17,6 @@ if __name__ == '__main__':
 
     for i in progress.dots(range(100)):
         sleep(random() * 0.2)
-    
+    
+    for i in progress.mill(range(100)):
+        sleep(random() * 0.2)