Print real part for complex even if it's zero

* adapt Lib/test/test_format.py and Lib/test/test_complex.py
* adjust doctests

Author: skirpichev

Doc/library/functions.rst

@@ -389,7 +389,7 @@ are always available.  They are listed here in alphabetical order.
       >>> complex('+1.23')
       (1.23+0j)
       >>> complex('-4.5j')
-      -4.5j
+      (0.0-4.5j)
       >>> complex('-1.23+4.5j')
       (-1.23+4.5j)
       >>> complex('\t( -1.23+4.5J )\n')
@@ -399,7 +399,7 @@ are always available.  They are listed here in alphabetical order.
       >>> complex(1.23)
       (1.23+0j)
       >>> complex(imag=-4.5)
-      -4.5j
+      (0.0-4.5j)
       >>> complex(-1.23, 4.5)
       (-1.23+4.5j)
 

Lib/test/test_complex.py

@@ -880,9 +880,13 @@ def test(v, expected, test_fn=self.assertEqual):
         test(complex(NAN, NAN), "(nan+nanj)")
         test(complex(-NAN, -NAN), "(nan+nanj)")
 
-        test(complex(0, INF), "infj")
-        test(complex(0, -INF), "-infj")
-        test(complex(0, NAN), "nanj")
+        test(complex(0, INF), "(0.0+infj)")
+        test(complex(0, -INF), "(0.0-infj)")
+        test(complex(0, NAN), "(0.0+nanj)")
+
+        test(imaginary(INF), "infj")
+        test(imaginary(-INF), "-infj")
+        test(imaginary(NAN), "nanj")
 
         self.assertEqual(1-6j,complex(repr(1-6j)))
         self.assertEqual(1+6j,complex(repr(1+6j)))
@@ -895,16 +899,22 @@ def test(v, expected, test_fn=self.assertEqual):
             test_fn(repr(v), expected)
             test_fn(str(v), expected)
 
-        test(complex(0., 1.),   "1j")
+        test(complex(0., 1.),   "(0.0+1j)")
         test(complex(-0., 1.),  "(-0.0+1j)")
-        test(complex(0., -1.),  "-1j")
+        test(complex(0., -1.),  "(0.0-1j)")
         test(complex(-0., -1.), "(-0.0-1j)")
 
-        test(complex(0., 0.),   "0j")
-        test(complex(0., -0.),  "-0j")
+        test(imaginary(+1.), "1j")
+        test(imaginary(-1.), "-1j")
+
+        test(complex(0., 0.),   "(0.0+0j)")
+        test(complex(0., -0.),  "(0.0-0j)")
         test(complex(-0., 0.),  "(-0.0+0j)")
         test(complex(-0., -0.), "(-0.0-0j)")
 
+        test(imaginary(+0.0), "0j")
+        test(imaginary(-0.0), "-0j")
+
     def test_pos(self):
         self.assertEqual(+(1+6j), 1+6j)
         self.assertEqual(+ComplexSubclass(1, 6), 1+6j)
@@ -1011,7 +1021,8 @@ def test_format(self):
         self.assertEqual(format(z, '3'), str(z))
 
         self.assertEqual(format(1+3j, 'g'), '1+3j')
-        self.assertEqual(format(3j, 'g'), '0+3j')
+        self.assertEqual(format(0+3j, 'g'), '0.0+3j')
+        self.assertEqual(format(3j, 'g'), '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')

Lib/test/test_format.py

@@ -595,10 +595,15 @@ def test_negative_zero(self):
         self.assertEqual(f"{-1.:+z.0f}", "-1")
         self.assertEqual(f"{-1.:-z.0f}", "-1")
 
-        self.assertEqual(f"{0.j:z.1f}", "0.0+0.0j")
-        self.assertEqual(f"{-0.j:z.1f}", "0.0+0.0j")
-        self.assertEqual(f"{.01j:z.1f}", "0.0+0.0j")
-        self.assertEqual(f"{-.01j:z.1f}", "0.0+0.0j")
+        self.assertEqual(f"{0.0+0.j:z.1f}", "0.0+0.0j")
+        self.assertEqual(f"{0.0-0.j:z.1f}", "0.0+0.0j")
+        self.assertEqual(f"{0.0+.01j:z.1f}", "0.0+0.0j")
+        self.assertEqual(f"{0.0-.01j:z.1f}", "0.0+0.0j")
+
+        self.assertEqual(f"{0.j:z.1f}", "0.0j")
+        self.assertEqual(f"{-0.j:z.1f}", "0.0j")
+        self.assertEqual(f"{.01j:z.1f}", "0.0j")
+        self.assertEqual(f"{-.01j:z.1f}", "0.0j")
 
         self.assertEqual(f"{-0.:z>6.1f}", "zz-0.0")  # test fill, esp. 'z' fill
         self.assertEqual(f"{-0.:z>z6.1f}", "zzz0.0")

Objects/complexobject.c

@@ -519,9 +519,8 @@ complex_repr(PyComplexObject *v)
     const char *lead = "";
     const char *tail = "";
 
-    if (v->cval.real == 0. && copysign(1.0, v->cval.real)==1.0) {
-        /* Real part is +0: just output the imaginary part and do not
-           include parens. */
+    if (PyImaginary_Check(v)) {
+        /* Just output the imaginary part and do not include parens. */
         re = "";
         im = PyOS_double_to_string(v->cval.imag, format_code,
                                    precision, 0, NULL);

Python/formatter_unicode.c

@@ -1271,7 +1271,7 @@ format_complex_internal(PyObject *value,
         /* Omitted type specifier. Should be like str(self). */
         type = 'r';
         default_precision = 0;
-        if (re == 0.0 && copysign(1.0, re) == 1.0)
+        if (PyImaginary_Check(value))
             skip_re = 1;
         else
             add_parens = 1;
@@ -1290,10 +1290,14 @@ format_complex_internal(PyObject *value,
     /* Cast "type", because if we're in unicode we need to pass an
        8-bit char. This is safe, because we've restricted what "type"
        can be. */
-    if (re == 0.0 && copysign(1.0, re) == -1.0)
+    if (re == 0.0) {
+        if (PyImaginary_Check(value)) {
+            skip_re = 1;
+        }
         re_buf = PyOS_double_to_string(re, (char)type, precision,
                                        flags | Py_DTSF_ADD_DOT_0,
                                        &re_float_type);
+    }
     else
         re_buf = PyOS_double_to_string(re, (char)type, precision, flags,
                                        &re_float_type);