Deprecate dates.{str,bytes}pdate2num.

anntzer · anntzer · commit ef3e89e1d00f · 2019-01-29T22:25:48.000+01:00
They are brittle against locale changes and there are replacements in
the stdlib (time.strpdate, also brittle against locale changes) or
elsewhere (dateutil.parser.parse, more robust), which also do not
convert to Matplotlib's internal date representation (as that's not
needed for plotting datetime data).
diff --git a/doc/api/next_api_changes/2018-01-31-AL.rst b/doc/api/next_api_changes/2018-01-31-AL.rst
@@ -0,0 +1,8 @@
+Deprecations
+````````````
+
+``dates.strpdate2num`` and ``dates.bytespdate2num`` are brittle in the
+presence of locale changes, and are deprecated.  Use standard datetime
+parsers such as `time.strptime` or `dateutil.parser.parse`, and additionally
+call `matplotlib.dates.date2num` if you insist on converting to Matplotlib's
+internal datetime representation; or use ``dates.datestr2num``.
diff --git a/examples/misc/load_converter.py b/examples/misc/load_converter.py
@@ -1,8 +1,10 @@
 """
 ==============
-Load Converter
+Load converter
 ==============
 
+This example demonstrates passing a custom converter to `numpy.genfromtxt` to
+extract dates from a CSV file.
 """
 
 import dateutil.parser
@@ -16,9 +18,9 @@
 
 data = np.genfromtxt(
     datafile, delimiter=',', names=True,
-    converters={0: lambda s: dates.date2num(dateutil.parser.parse(s))})
+    dtype=None, converters={0: dateutil.parser.parse})
 
 fig, ax = plt.subplots()
-ax.plot_date(data['Date'], data['High'], '-')
+ax.plot(data['Date'], data['High'], '-')
 fig.autofmt_xdate()
 plt.show()
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -317,6 +317,8 @@ def _from_ordinalf(x, tz=None):
 _from_ordinalf_np_vectorized = np.vectorize(_from_ordinalf)
 
 
+@cbook.deprecated(
+    "3.1", alternative="time.strptime or dateutil.parser.parse or datestr2num")
 class strpdate2num(object):
     """
     Use this class to parse date strings to matplotlib datenums when
@@ -333,6 +335,8 @@ def __call__(self, s):
         return date2num(datetime.datetime(*time.strptime(s, self.fmt)[:6]))
 
 
+@cbook.deprecated(
+    "3.1", alternative="time.strptime or dateutil.parser.parse or datestr2num")
 class bytespdate2num(strpdate2num):
     """
     Use this class to parse date strings to matplotlib datenums when
