bpo-28240: timeit: Update repeat() doc (GH-7419)

Document that the default value of repeat changed from 3 to 5 in
Python 3.7.

Author: vstinner

Doc/library/timeit.rst

@@ -69,7 +69,7 @@ The module defines three convenience functions and a public class:
       The optional *globals* parameter was added.
 
 
-.. function:: repeat(stmt='pass', setup='pass', timer=<default timer>, repeat=3, number=1000000, globals=None)
+.. function:: repeat(stmt='pass', setup='pass', timer=<default timer>, repeat=5, number=1000000, globals=None)
 
    Create a :class:`Timer` instance with the given statement, *setup* code and
    *timer* function and run its :meth:`.repeat` method with the given *repeat*
@@ -79,6 +79,9 @@ The module defines three convenience functions and a public class:
    .. versionchanged:: 3.5
       The optional *globals* parameter was added.
 
+   .. versionchanged:: 3.7
+      Default value of *repeat* changed from 3 to 5.
+
 .. function:: default_timer()
 
    The default timer, which is always :func:`time.perf_counter`.
@@ -150,7 +153,7 @@ The module defines three convenience functions and a public class:
       .. versionadded:: 3.6
 
 
-   .. method:: Timer.repeat(repeat=3, number=1000000)
+   .. method:: Timer.repeat(repeat=5, number=1000000)
 
       Call :meth:`.timeit` a few times.
 
@@ -171,6 +174,9 @@ The module defines three convenience functions and a public class:
          should be interested in.  After that, you should look at the entire
          vector and apply common sense rather than statistics.
 
+      .. versionchanged:: 3.7
+         Default value of *repeat* changed from 3 to 5.
+
 
    .. method:: Timer.print_exc(file=None)
 
@@ -208,7 +214,7 @@ Where the following options are understood:
 
 .. cmdoption:: -r N, --repeat=N
 
-   how many times to repeat the timer (default 3)
+   how many times to repeat the timer (default 5)
 
 .. cmdoption:: -s S, --setup=S
 
@@ -246,7 +252,7 @@ successive powers of 10 until the total time is at least 0.2 seconds.
 :func:`default_timer` measurements can be affected by other programs running on
 the same machine, so the best thing to do when accurate timing is necessary is
 to repeat the timing a few times and use the best time.  The :option:`-r`
-option is good for this; the default of 3 repetitions is probably enough in
+option is good for this; the default of 5 repetitions is probably enough in
 most cases.  You can use :func:`time.process_time` to measure CPU time.
 
 .. note::

Lib/timeit.py

@@ -13,7 +13,7 @@
 
 Options:
   -n/--number N: how many times to execute 'statement' (default: see below)
-  -r/--repeat N: how many times to repeat the timer (default 3)
+  -r/--repeat N: how many times to repeat the timer (default 5)
   -s/--setup S: statement to be executed once initially (default 'pass').
                 Execution time of this setup statement is NOT timed.
   -p/--process: use time.process_time() (default is time.perf_counter())
@@ -184,7 +184,7 @@ def repeat(self, repeat=default_repeat, number=default_number):
 
         This is a convenience function that calls the timeit()
         repeatedly, returning a list of results.  The first argument
-        specifies how many times to call timeit(), defaulting to 3;
+        specifies how many times to call timeit(), defaulting to 5;
         the second argument specifies the timer argument, defaulting
         to one million.