add dt.timer which can time how long does calling take as a context manager or decorator.

pydu/dt.py

@@ -0,0 +1,30 @@
+import time
+
+
+class timer(object):
+    """
+    A timer can time how long does calling take as a context manager or decorator.
+    If assign ``print_func`` with ``sys.stdout.write``, ``logger.info`` and so on,
+    timer will print the spent time.
+    """
+
+    def __init__(self, print_func=None):
+        self.elapsed = None
+        self.print_func = print_func
+
+    def __enter__(self):
+        self.start = time.time()
+
+    def __exit__(self, *_):
+        self.elapsed = time.time() - self.start
+        if self.print_func:
+            self.print_func(self.__str__())
+
+    def __call__(self, fun):
+        def wrapper(*args, **kwargs):
+            with self:
+                return fun(*args, **kwargs)
+        return wrapper
+
+    def __str__(self):
+        return 'Spent time: {}s'.format(self.elapsed)