bpo-36546: Mark first argument as position only (GH-14363)

Author: rhettinger

Lib/statistics.py

@@ -603,7 +603,7 @@ def multimode(data):
 # options make for easier choices and that external packages can be
 # used for anything more advanced.
 
-def quantiles(dist, *, n=4, method='exclusive'):
+def quantiles(dist, /, *, n=4, method='exclusive'):
     '''Divide *dist* into *n* continuous intervals with equal probability.
 
     Returns a list of (n - 1) cut points separating the intervals.

Misc/NEWS.d/next/Library/2019-06-25-05-07-48.bpo-36546.RUcxaK.rst

@@ -0,0 +1,4 @@
+The *dist* argument for statistics.quantiles() is now positional only. The
+current name doesn't reflect that the argument can be either a dataset or a
+distribution.  Marking the parameter as positional avoids confusion and
+makes it possible to change the name later.