ENH: fix 0d array printing using `str` or `formatter`.

The str of 0d arrays now returns `str(a[()])` like scalars, and the
repr returns `'array(' + formatter(a[()]) + ')'` like ndarrays.
The default implementation of str and repr for user-defined types is
removed. Fixes #1415

1 files changed, 12 insertions, 15 deletions

diff --git a/numpy/core/arrayprint.py b/numpy/core/arrayprint.py
index 2706d16f0..f996aa394 100644
--- a/numpy/core/arrayprint.py
+++ b/numpy/core/arrayprint.py
@@ -416,8 +416,8 @@ def _array2string(a, options, separator=' ', prefix=""):
 
 def array2string(a, max_line_width=None, precision=None,
                  suppress_small=None, separator=' ', prefix="",
-                 style=np._NoValue, formatter=None, threshold=None,
-                 edgeitems=None, sign=None, floatmode=None):
+                 style=None, formatter=None, threshold=None,
+                 edgeitems=None, sign=None):
     """
     Return a string representation of an array.
 
@@ -441,12 +441,11 @@ def array2string(a, max_line_width=None, precision=None,
 
           'prefix(' + array2string(a) + ')'
 
-        The length of the prefix string is used to align the
-        output correctly.
-    style : _NoValue, optional
-        Has no effect, do not use.
-
-        .. deprecated:: 1.14.0
+        The length of the prefix string is used to align the output correctly.
+    style : None or function, optional
+        Controls the printing of 0d arrays. If `None`, prints the 0d array's
+        element using the usual array formatting. Otherwise, `style` should be
+        a function that accepts a numpy scalar and returns a string.
     formatter : dict of callables, optional
         If not None, the keys should indicate the type(s) that the respective
         formatting function applies to.  Callables should return a string.
@@ -541,18 +540,15 @@ def array2string(a, max_line_width=None, precision=None,
     '[0x0L 0x1L 0x2L]'
 
     """
-    # Deprecation 05-16-2017  v1.14
-    if style is not np._NoValue:
-        warnings.warn("'style' argument is deprecated and no longer functional",
-                      DeprecationWarning, stacklevel=3)
-
     overrides = _make_options_dict(precision, threshold, edgeitems,
                                    max_line_width, suppress_small, None, None,
                                    sign, formatter, floatmode)
     options = _format_options.copy()
     options.update(overrides)
 
-    if a.size == 0:
+    if style is not None and a.shape == ():
+        return style(a[()])
+    elif a.size == 0:
         # treat as a null array if any of shape elements == 0
         lst = "[]"
     else:
@@ -1164,7 +1160,8 @@ def array_str(a, max_line_width=None, precision=None, suppress_small=None):
     '[0 1 2]'
 
     """
-    return array2string(a, max_line_width, precision, suppress_small, ' ', "")
+    return array2string(a, max_line_width, precision, suppress_small,
+                        ' ', "", str)
 
 def set_string_function(f, repr=True):
     """