(although some languages may not *display* the difference by default, or in all
output modes).
-Python's built-in :func:`str` function produces only 12 significant digits, and
-you may wish to use that instead. It's unusual for ``eval(str(x))`` to
-reproduce *x*, but the output may be more pleasant to look at::
+For more pleasant output, you may may wish to use string formatting to produce a limited number of significant digits::
- >>> str(math.pi)
+ >>> format(math.pi, '.12g') # give 12 significant digits
'3.14159265359'
+ >>> format(math.pi, '.2f') # give 2 digits after the point
+ '3.14'
+
>>> repr(math.pi)
'3.141592653589793'
- >>> format(math.pi, '.2f')
- '3.14'
It's important to realize that this is, in a real sense, an illusion: you're
simply rounding the *display* of the true machine value.
#define PyFloat_Check(op) PyObject_TypeCheck(op, &PyFloat_Type)
#define PyFloat_CheckExact(op) (Py_TYPE(op) == &PyFloat_Type)
-/* The str() precision PyFloat_STR_PRECISION is chosen so that in most cases,
- the rounding noise created by various operations is suppressed, while
- giving plenty of precision for practical use. */
-
-#define PyFloat_STR_PRECISION 12
-
#ifdef Py_NAN
#define Py_RETURN_NAN return PyFloat_FromDouble(Py_NAN)
#endif
%#.5g 234.56 -> 234.56
%#.6g 234.56 -> 234.560
--- for repr formatting see the separate test_short_repr test in
--- test_float.py. Not all platforms use short repr for floats.
-
--- str formatting. Result always includes decimal point and at
+-- repr formatting. Result always includes decimal point and at
-- least one digit after the point, or an exponent.
-%s 0 -> 0.0
-%s 1 -> 1.0
-
-%s 0.01 -> 0.01
-%s 0.02 -> 0.02
-%s 0.03 -> 0.03
-%s 0.04 -> 0.04
-%s 0.05 -> 0.05
+%r 0 -> 0.0
+%r 1 -> 1.0
--- str truncates to 12 significant digits
-%s 1.234123412341 -> 1.23412341234
-%s 1.23412341234 -> 1.23412341234
-%s 1.2341234123 -> 1.2341234123
+%r 0.01 -> 0.01
+%r 0.02 -> 0.02
+%r 0.03 -> 0.03
+%r 0.04 -> 0.04
+%r 0.05 -> 0.05
--- values >= 1e11 get an exponent
-%s 10 -> 10.0
-%s 100 -> 100.0
-%s 1e10 -> 10000000000.0
-%s 9.999e10 -> 99990000000.0
-%s 99999999999 -> 99999999999.0
-%s 99999999999.9 -> 99999999999.9
-%s 99999999999.99 -> 1e+11
-%s 1e11 -> 1e+11
-%s 1e12 -> 1e+12
+-- values >= 1e16 get an exponent
+%r 10 -> 10.0
+%r 100 -> 100.0
+%r 1e15 -> 1000000000000000.0
+%r 9.999e15 -> 9999000000000000.0
+%r 9999999999999998 -> 9999999999999998.0
+%r 9999999999999999 -> 1e+16
+%r 1e16 -> 1e+16
+%r 1e17 -> 1e+17
-- as do values < 1e-4
-%s 1e-3 -> 0.001
-%s 1.001e-4 -> 0.0001001
-%s 1.000000000001e-4 -> 0.0001
-%s 1.00000000001e-4 -> 0.000100000000001
-%s 1.0000000001e-4 -> 0.00010000000001
-%s 1e-4 -> 0.0001
-%s 0.999999999999e-4 -> 9.99999999999e-05
-%s 0.999e-4 -> 9.99e-05
-%s 1e-5 -> 1e-05
+%r 1e-3 -> 0.001
+%r 1.001e-4 -> 0.0001001
+%r 1.0000000000000001e-4 -> 0.0001
+%r 1.000000000000001e-4 -> 0.0001000000000000001
+%r 1.00000000001e-4 -> 0.000100000000001
+%r 1.0000000001e-4 -> 0.00010000000001
+%r 1e-4 -> 0.0001
+%r 0.99999999999999999e-4 -> 0.0001
+%r 0.9999999999999999e-4 -> 9.999999999999999e-05
+%r 0.999999999999e-4 -> 9.99999999999e-05
+%r 0.999e-4 -> 9.99e-05
+%r 1e-5 -> 1e-05
negs = '-'+s
self.assertEqual(s, repr(float(s)))
self.assertEqual(negs, repr(float(negs)))
-
+ # Since Python 3.2, repr and str are identical
+ self.assertEqual(repr(float(s)), str(float(s)))
+ self.assertEqual(repr(float(negs)), str(float(negs)))
@requires_IEEE_754
class RoundTestCase(unittest.TestCase):
The format of the exponent is inherited from the platform C library.
Known cases are "e-007" (Windows) and "e-07" (not Windows). Since
- we're only showing 12 digits, and the 13th isn't close to 5, the
+ we're only showing 11 digits, and the 12th isn't close to 5, the
rest of the output should be platform-independent.
>>> exec(s) #doctest: +ELLIPSIS
- -3.21716034272e-0...7
+ -3.2171603427...e-0...7
Output from calculations with Decimal should be identical across all
platforms.
class UnicodeFunctionsTest(UnicodeDatabaseTest):
# update this, if the database changes
- expectedchecksum = '6ccf1b1a36460d2694f9b0b0f0324942fe70ede6'
-
+ expectedchecksum = 'e89a6380093a00a7685ac7b92e7367d737fcb79b'
def test_function_checksum(self):
data = []
h = hashlib.sha1()
char = chr(i)
data = [
# Properties
- str(self.db.digit(char, -1)),
- str(self.db.numeric(char, -1)),
- str(self.db.decimal(char, -1)),
+ format(self.db.digit(char, -1), '.12g'),
+ format(self.db.numeric(char, -1), '.12g'),
+ format(self.db.decimal(char, -1), '.12g'),
self.db.category(char),
self.db.bidirectional(char),
self.db.decomposition(char),
Core and Builtins
-----------------
+- Issue #9337: The str() of a float or complex number is now identical
+ to its repr().
+
- Issue #9416: Fix some issues with complex formatting where the
output with no type specifier failed to match the str output:
return complex_format(v, 0, 'r');
}
-static PyObject *
-complex_str(PyComplexObject *v)
-{
- return complex_format(v, PyFloat_STR_PRECISION, 'g');
-}
-
static long
complex_hash(PyComplexObject *v)
{
0, /* tp_as_mapping */
(hashfunc)complex_hash, /* tp_hash */
0, /* tp_call */
- (reprfunc)complex_str, /* tp_str */
+ (reprfunc)complex_repr, /* tp_str */
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
}
static PyObject *
-float_str_or_repr(PyFloatObject *v, int precision, char format_code)
+float_repr(PyFloatObject *v)
{
PyObject *result;
char *buf = PyOS_double_to_string(PyFloat_AS_DOUBLE(v),
- format_code, precision,
+ 'r', 0,
Py_DTSF_ADD_DOT_0,
NULL);
if (!buf)
- return PyErr_NoMemory();
+ return PyErr_NoMemory();
result = PyUnicode_FromString(buf);
PyMem_Free(buf);
return result;
}
-static PyObject *
-float_repr(PyFloatObject *v)
-{
- return float_str_or_repr(v, 0, 'r');
-}
-
-static PyObject *
-float_str(PyFloatObject *v)
-{
- return float_str_or_repr(v, PyFloat_STR_PRECISION, 'g');
-}
-
/* Comparison is pretty much a nightmare. When comparing float to float,
* we do it as straightforwardly (and long-windedly) as conceivable, so
* that, e.g., Python x == y delivers the same result as the platform
CONVERT_TO_DOUBLE(v, x);
if (Py_IS_NAN(x) || Py_IS_INFINITY(x))
- return float_str((PyFloatObject *)v);
+ return float_repr((PyFloatObject *)v);
if (x == 0.0) {
if (copysign(1.0, x) == -1.0)
0, /* tp_as_mapping */
(hashfunc)float_hash, /* tp_hash */
0, /* tp_call */
- (reprfunc)float_str, /* tp_str */
+ (reprfunc)float_repr, /* tp_str */
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
}
if (type == '\0') {
- /* Omitted type specifier. This is like 'g' but with at least one
- digit after the decimal point, and different default precision.*/
- type = 'g';
- default_precision = PyFloat_STR_PRECISION;
+ /* Omitted type specifier. Behaves in the same way as repr(x)
+ and str(x) if no precision is given, else like 'g', but with
+ at least one digit after the decimal point. */
flags |= Py_DTSF_ADD_DOT_0;
+ type = 'r';
+ default_precision = 0;
}
if (type == 'n')
if (precision < 0)
precision = default_precision;
+ else if (type == 'r')
+ type = 'g';
/* Cast "type", because if we're in unicode we need to pass a
8-bit char. This is safe, because we've restricted what "type"
if (type == '\0') {
/* Omitted type specifier. Should be like str(self). */
- type = 'g';
- default_precision = PyFloat_STR_PRECISION;
+ type = 'r';
+ default_precision = 0;
if (re == 0.0 && copysign(1.0, re) == 1.0)
skip_re = 1;
else
if (precision < 0)
precision = default_precision;
+ else if (type == 'r')
+ type = 'g';
/* Cast "type", because if we're in unicode we need to pass a
8-bit char. This is safe, because we've restricted what "type"
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