Add pretty_dps context property to control number of printed digits

Closes #921

docs/basics.rst

@@ -221,6 +221,8 @@ Setting the ``mp.pretty`` option will use the ``str()``-style output for ``repr(
     >>> mpf(0.6)
     mpf('0.59999999999999998')
 
+To use enough digits to be able recreate value exactly, set ``mp.pretty_dps`` to ``"repr"``.
+
 The number of digits with which numbers are printed by default is determined by
 the working precision.  To specify the number of digits to show without
 changing the working precision, use :func:`format syntax support

mpmath/__main__.py

@@ -57,6 +57,7 @@ def main():
         lines.append(f'mp.prec = {args.prec}')
     if not args.no_pretty:
         lines.append('mp.pretty = True')
+        lines.append('mp.pretty_dps = "repr"')
 
     try:
         import IPython

mpmath/ctx_mp_python.py

@@ -130,7 +130,9 @@ class _mpf(mpnumeric):
 
     def __repr__(s):
         if s.context.pretty:
-            return str(s)
+            ndigits = (s.context._repr_digits
+                       if s.context._pretty_repr_dps else s.context._str_digits)
+            return to_str(s._mpf_, ndigits)
         return "mpf('%s')" % to_str(s._mpf_, s.context._repr_digits)
 
     def __str__(s): return to_str(s._mpf_, s.context._str_digits)
@@ -514,7 +516,9 @@ class _mpc(mpnumeric):
 
     def __repr__(s):
         if s.context.pretty:
-            return str(s)
+            ndigits = (s.context._repr_digits
+                       if s.context._pretty_repr_dps else s.context._str_digits)
+            return "(%s)" % mpc_to_str(s._mpc_, ndigits)
         r = repr(s.real)[4:-1]
         i = repr(s.imag)[4:-1]
         return "%s(real=%s, imag=%s)" % (type(s).__name__, r, i)
@@ -709,6 +713,7 @@ class PythonMPContext:
         ctx.constant = type('constant', (_constant,), {})
         ctx.constant._ctxdata = [ctx.mpf, new, ctx._prec_rounding]
         ctx.constant.context = ctx
+        ctx._pretty_repr_dps = False
 
     def make_mpf(ctx, v):
         a = new(ctx.mpf)
@@ -736,6 +741,14 @@ class PythonMPContext:
     prec = property(lambda ctx: ctx._prec, _set_prec)
     dps = property(lambda ctx: ctx._dps, _set_dps)
 
+    def _set_pretty_dps(ctx, v):
+        ctx._pretty_repr_dps = True if v == 'repr' else False
+
+    def _get_pretty_dps(ctx):
+        return 'repr' if ctx._pretty_repr_dps else 'str'
+
+    pretty_dps = property(_get_pretty_dps, _set_pretty_dps)
+
     def convert(ctx, x, strings=True):
         """
         Converts *x* to an ``mpf`` or ``mpc``. If *x* is of type ``mpf``,

mpmath/tests/test_cli.py

@@ -111,7 +111,7 @@ def test_bare_console_pretty():
 
     assert c.expect_exact('>>> ') == 0
     assert c.send("10.9\r\n") == 6
-    assert c.expect_exact("10.9\r\n>>> ") == 0
+    assert c.expect_exact("10.899999999999999999999999999995\r\n>>> ") == 0
     assert c.send("def f():\r\n  x = ?\r\n\r\n") == 21
     assert c.expect('SyntaxError:') == 0