Issue #1588: Add complex.__format__.

Include/complexobject.h

@@ -54,6 +54,12 @@ PyAPI_FUNC(double) PyComplex_RealAsDouble(PyObject *op);
 PyAPI_FUNC(double) PyComplex_ImagAsDouble(PyObject *op);
 PyAPI_FUNC(Py_complex) PyComplex_AsCComplex(PyObject *op);
 
+/* Format the object based on the format_spec, as defined in PEP 3101
+   (Advanced String Formatting). */
+PyAPI_FUNC(PyObject *) _PyComplex_FormatAdvanced(PyObject *obj,
+                                                 Py_UNICODE *format_spec,
+                                                 Py_ssize_t format_spec_len);
+
 #ifdef __cplusplus
 }
 #endif

Lib/test/test_complex.py

@@ -436,7 +436,66 @@ class ComplexTest(unittest.TestCase):
                 self.assertFloatsAreIdentical(0.0 + z.imag,
                                               0.0 + roundtrip.imag)
 
-
+    def test_format(self):
+        # empty format string is same as str()
+        self.assertEqual(format(1+3j, ''), str(1+3j))
+        self.assertEqual(format(1.5+3.5j, ''), str(1.5+3.5j))
+        self.assertEqual(format(3j, ''), str(3j))
+        self.assertEqual(format(3.2j, ''), str(3.2j))
+        self.assertEqual(format(3+0j, ''), str(3+0j))
+        self.assertEqual(format(3.2+0j, ''), str(3.2+0j))
+
+        self.assertEqual(format(1+3j, 'g'), '1+3j')
+        self.assertEqual(format(3j, 'g'), '0+3j')
+        self.assertEqual(format(1.5+3.5j, 'g'), '1.5+3.5j')
+
+        self.assertEqual(format(1.5+3.5j, '+g'), '+1.5+3.5j')
+        self.assertEqual(format(1.5-3.5j, '+g'), '+1.5-3.5j')
+        self.assertEqual(format(1.5-3.5j, '-g'), '1.5-3.5j')
+        self.assertEqual(format(1.5+3.5j, ' g'), ' 1.5+3.5j')
+        self.assertEqual(format(1.5-3.5j, ' g'), ' 1.5-3.5j')
+        self.assertEqual(format(-1.5+3.5j, ' g'), '-1.5+3.5j')
+        self.assertEqual(format(-1.5-3.5j, ' g'), '-1.5-3.5j')
+
+        self.assertEqual(format(-1.5-3.5e-20j, 'g'), '-1.5-3.5e-20j')
+        self.assertEqual(format(-1.5-3.5j, 'f'), '-1.500000-3.500000j')
+        self.assertEqual(format(-1.5-3.5j, 'F'), '-1.500000-3.500000j')
+        self.assertEqual(format(-1.5-3.5j, 'e'), '-1.500000e+00-3.500000e+00j')
+        self.assertEqual(format(-1.5-3.5j, '.2e'), '-1.50e+00-3.50e+00j')
+        self.assertEqual(format(-1.5-3.5j, '.2E'), '-1.50E+00-3.50E+00j')
+        self.assertEqual(format(-1.5e10-3.5e5j, '.2G'), '-1.5E+10-3.5E+05j')
+
+        self.assertEqual(format(1.5+3j, '<20g'),  '1.5+3j              ')
+        self.assertEqual(format(1.5+3j, '*<20g'), '1.5+3j**************')
+        self.assertEqual(format(1.5+3j, '>20g'),  '              1.5+3j')
+        self.assertEqual(format(1.5+3j, '^20g'),  '       1.5+3j       ')
+        self.assertEqual(format(1.5+3j, '<20'),   '(1.5+3j)            ')
+        self.assertEqual(format(1.5+3j, '>20'),   '            (1.5+3j)')
+        self.assertEqual(format(1.5+3j, '^20'),   '      (1.5+3j)      ')
+        self.assertEqual(format(1.123-3.123j, '^20.2'), '     (1.1-3.1j)     ')
+
+        self.assertEqual(format(1.5+3j, '<20.2f'), '1.50+3.00j          ')
+        self.assertEqual(format(1.5e20+3j, '<20.2f'), '150000000000000000000.00+3.00j')
+        self.assertEqual(format(1.5e20+3j, '>40.2f'), '          150000000000000000000.00+3.00j')
+        self.assertEqual(format(1.5e20+3j, '^40,.2f'), '  150,000,000,000,000,000,000.00+3.00j  ')
+        self.assertEqual(format(1.5e21+3j, '^40,.2f'), ' 1,500,000,000,000,000,000,000.00+3.00j ')
+        self.assertEqual(format(1.5e21+3000j, ',.2f'), '1,500,000,000,000,000,000,000.00+3,000.00j')
+
+        # alternate is invalid
+        self.assertRaises(ValueError, (1.5+0.5j).__format__, '#f')
+
+        # zero padding is invalid
+        self.assertRaises(ValueError, (1.5+0.5j).__format__, '010f')
+
+        # '=' alignment is invalid
+        self.assertRaises(ValueError, (1.5+3j).__format__, '=20')
+
+        # integer presentation types are an error
+        for t in 'bcdoxX':
+            self.assertRaises(ValueError, (1.5+0.5j).__format__, t)
+
+        # make sure everything works in ''.format()
+        self.assertEqual('*{0:.3f}*'.format(3.14159+2.71828j), '*3.142+2.718j*')
 
 def test_main():
     support.run_unittest(ComplexTest)

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 3.1 beta 1?
 Core and Builtins
 -----------------
 
+- Issue #1588: Add complex.__format__. For example, 
+  format(complex(1, 2./3), '.5') now produces a sensible result.
+
 - Issue #5864: Fix empty format code formatting for floats so that it
   never gives more than the requested number of significant digits.
 

Objects/complexobject.c

@@ -681,6 +681,23 @@ complex_getnewargs(PyComplexObject *v)
 	return Py_BuildValue("(dd)", c.real, c.imag);
 }
 
+PyDoc_STRVAR(complex__format__doc,
+"complex.__format__() -> str\n"
+"\n"
+"Converts to a string according to format_spec.");
+
+static PyObject *
+complex__format__(PyObject* self, PyObject* args)
+{
+    PyObject *format_spec;
+
+    if (!PyArg_ParseTuple(args, "U:__format__", &format_spec))
+        return NULL;
+    return _PyComplex_FormatAdvanced(self,
+                                     PyUnicode_AS_UNICODE(format_spec),
+                                     PyUnicode_GET_SIZE(format_spec));
+}
+
 #if 0
 static PyObject *
 complex_is_finite(PyObject *self)
@@ -705,6 +722,8 @@ static PyMethodDef complex_methods[] = {
 	 complex_is_finite_doc},
 #endif
 	{"__getnewargs__",	(PyCFunction)complex_getnewargs,	METH_NOARGS},
+	{"__format__",          (PyCFunction)complex__format__,
+                                           METH_VARARGS, complex__format__doc},
 	{NULL,		NULL}		/* sentinel */
 };
 

Python/formatter_unicode.c

@@ -6,8 +6,9 @@
 #include "../Objects/stringlib/unicodedefs.h"
 
 
-#define FORMAT_STRING _PyUnicode_FormatAdvanced
-#define FORMAT_LONG   _PyLong_FormatAdvanced
-#define FORMAT_FLOAT  _PyFloat_FormatAdvanced
+#define FORMAT_STRING  _PyUnicode_FormatAdvanced
+#define FORMAT_LONG    _PyLong_FormatAdvanced
+#define FORMAT_FLOAT   _PyFloat_FormatAdvanced
+#define FORMAT_COMPLEX _PyComplex_FormatAdvanced
 
 #include "../Objects/stringlib/formatter.h"