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authorChristian Heimes <christian@cheimes.de>2008-02-16 07:38:31 (GMT)
committerChristian Heimes <christian@cheimes.de>2008-02-16 07:38:31 (GMT)
commita156e09b19cd239176a9316ddca7641784eea99e (patch)
tree0aa8388d9496bbc7a0425f317007ab69e8049c70 /Doc/library
parent71316b0378d57a8ffe9733339318c8bdaccb706b (diff)
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Merged revisions 60481,60485,60489-60492,60494-60496,60498-60499,60501-60503,60505-60506,60508-60509,60523-60524,60532,60543,60545,60547-60548,60552,60554,60556-60559,60561-60562,60569,60571-60572,60574,60576-60583,60585-60586,60589,60591,60594-60595,60597-60598,60600-60601,60606-60612,60615,60617,60619-60621,60623-60625,60627-60629,60631,60633,60635,60647,60650,60652,60654,60656,60658-60659,60664-60666,60668-60670,60672,60676,60678,60680-60683,60685-60686,60688,60690,60692-60694,60697-60700,60705-60706,60708,60711,60714,60720,60724-60730,60732,60736,60742,60744,60746,60748,60750-60751,60753,60756-60757,60759-60761,60763-60764,60766,60769-60770,60774-60784,60787-60845 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk ........ r60790 | raymond.hettinger | 2008-02-14 10:32:45 +0100 (Thu, 14 Feb 2008) | 4 lines Add diagnostic message to help figure-out why SocketServer tests occasionally crash when trying to remove a pid that in not in the activechildren list. ........ r60791 | raymond.hettinger | 2008-02-14 11:46:57 +0100 (Thu, 14 Feb 2008) | 1 line Add fixed-point examples to the decimal FAQ ........ r60792 | raymond.hettinger | 2008-02-14 12:01:10 +0100 (Thu, 14 Feb 2008) | 1 line Improve rst markup ........ r60794 | raymond.hettinger | 2008-02-14 12:57:25 +0100 (Thu, 14 Feb 2008) | 1 line Show how to remove exponents. ........ r60795 | raymond.hettinger | 2008-02-14 13:05:42 +0100 (Thu, 14 Feb 2008) | 1 line Fix markup. ........ r60797 | christian.heimes | 2008-02-14 13:47:33 +0100 (Thu, 14 Feb 2008) | 1 line Implemented Martin's suggestion to clear the free lists during the garbage collection of the highest generation. ........ r60798 | raymond.hettinger | 2008-02-14 13:49:37 +0100 (Thu, 14 Feb 2008) | 1 line Simplify moneyfmt() recipe. ........ r60810 | raymond.hettinger | 2008-02-14 20:02:39 +0100 (Thu, 14 Feb 2008) | 1 line Fix markup ........ r60811 | raymond.hettinger | 2008-02-14 20:30:30 +0100 (Thu, 14 Feb 2008) | 1 line No need to register subclass of ABCs. ........ r60814 | thomas.heller | 2008-02-14 22:00:28 +0100 (Thu, 14 Feb 2008) | 1 line Try to correct a markup error that does hide the following paragraph. ........ r60822 | christian.heimes | 2008-02-14 23:40:11 +0100 (Thu, 14 Feb 2008) | 1 line Use a static and interned string for __subclasscheck__ and __instancecheck__ as suggested by Thomas Heller in #2115 ........ r60827 | christian.heimes | 2008-02-15 07:57:08 +0100 (Fri, 15 Feb 2008) | 1 line Fixed repr() and str() of complex numbers. Complex suffered from the same problem as floats but I forgot to test and fix them. ........ r60830 | christian.heimes | 2008-02-15 09:20:11 +0100 (Fri, 15 Feb 2008) | 2 lines Bug #2111: mmap segfaults when trying to write a block opened with PROT_READ Thanks to Thomas Herve for the fix. ........ r60835 | eric.smith | 2008-02-15 13:14:32 +0100 (Fri, 15 Feb 2008) | 1 line In PyNumber_ToBase, changed from an assert to returning an error when PyObject_Index() returns something other than an int or long. It should never be possible to trigger this, as PyObject_Index checks to make sure it returns an int or long. ........ r60837 | skip.montanaro | 2008-02-15 20:03:59 +0100 (Fri, 15 Feb 2008) | 8 lines Two new functions: * place_summary_first copies the regrtest summary to the front of the file making it easier to scan quickly for problems. * count_failures gets the actual count of the number of failing tests, not just a 1 (some failures) or 0 (no failures). ........ r60840 | raymond.hettinger | 2008-02-15 22:21:25 +0100 (Fri, 15 Feb 2008) | 1 line Update example to match the current syntax. ........ r60841 | amaury.forgeotdarc | 2008-02-15 22:22:45 +0100 (Fri, 15 Feb 2008) | 8 lines Issue #2115: __slot__ attributes setting was 10x slower. Also correct a possible crash using ABCs. This change is exactly the same as an optimisation done 5 years ago, but on slot *access*: http://svn.python.org/view?view=rev&rev=28297 ........ r60842 | amaury.forgeotdarc | 2008-02-15 22:27:44 +0100 (Fri, 15 Feb 2008) | 2 lines Temporarily let these tests pass ........ r60843 | kurt.kaiser | 2008-02-15 22:56:36 +0100 (Fri, 15 Feb 2008) | 2 lines ScriptBinding event handlers weren't returning 'break'. Patch 2050, Tal Einat. ........ r60844 | kurt.kaiser | 2008-02-15 23:25:09 +0100 (Fri, 15 Feb 2008) | 4 lines Configured selection highlighting colors were ignored; updating highlighting in the config dialog would cause non-Python files to be colored as if they were Python source; improve use of ColorDelagator. Patch 1334. Tal Einat. ........ r60845 | amaury.forgeotdarc | 2008-02-15 23:44:20 +0100 (Fri, 15 Feb 2008) | 9 lines Re-enable tests, they were failing since gc.collect() clears the various freelists. They still remain fragile. For example, a call to assertEqual currently does not make any allocation (which surprised me at first). But this can change when gc.collect also deletes the numerous "zombie frames" attached to each function. ........
Diffstat (limited to 'Doc/library')
-rw-r--r--Doc/library/ctypes.rst1
-rw-r--r--Doc/library/decimal.rst63
2 files changed, 46 insertions, 18 deletions
diff --git a/Doc/library/ctypes.rst b/Doc/library/ctypes.rst
index 3c305ed..b2d672f 100644
--- a/Doc/library/ctypes.rst
+++ b/Doc/library/ctypes.rst
@@ -2010,7 +2010,6 @@ Fundamental data types
their methods and attributes.
.. versionchanged:: 2.6
-
ctypes data types that are not and do not contain pointers can
now be pickled.
diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst
index afba964..b0845e9 100644
--- a/Doc/library/decimal.rst
+++ b/Doc/library/decimal.rst
@@ -1352,19 +1352,15 @@ to work with the :class:`Decimal` class::
'<.02>'
"""
- q = Decimal((0, (1,), -places)) # 2 places --> '0.01'
- sign, digits, exp = value.quantize(q).as_tuple()
- assert exp == -places
+ q = Decimal(10) ** -places # 2 places --> '0.01'
+ sign, digits, exp = value.quantize(q).as_tuple()
result = []
digits = map(str, digits)
build, next = result.append, digits.pop
if sign:
build(trailneg)
for i in range(places):
- if digits:
- build(next())
- else:
- build('0')
+ build(next() if digits else '0')
build(dp)
i = 0
while digits:
@@ -1374,12 +1370,8 @@ to work with the :class:`Decimal` class::
i = 0
build(sep)
build(curr)
- if sign:
- build(neg)
- else:
- build(pos)
- result.reverse()
- return ''.join(result)
+ build(neg if sign else pos)
+ return ''.join(reversed(result))
def pi():
"""Compute Pi to the current precision.
@@ -1482,7 +1474,7 @@ Decimal FAQ
Q. It is cumbersome to type ``decimal.Decimal('1234.5')``. Is there a way to
minimize typing when using the interactive interpreter?
-\A. Some users abbreviate the constructor to just a single letter::
+A. Some users abbreviate the constructor to just a single letter::
>>> D = decimal.Decimal
>>> D('1.23') + D('3.45')
@@ -1513,9 +1505,36 @@ the :const:`Inexact` trap is set, it is also useful for validation::
Q. Once I have valid two place inputs, how do I maintain that invariant
throughout an application?
-A. Some operations like addition and subtraction automatically preserve fixed
-point. Others, like multiplication and division, change the number of decimal
-places and need to be followed-up with a :meth:`quantize` step.
+A. Some operations like addition, subtraction, and multiplication by an integer
+will automatically preserve fixed point. Others operations, like division and
+non-integer multiplication, will change the number of decimal places and need to
+be followed-up with a :meth:`quantize` step::
+
+ >>> a = Decimal('102.72') # Initial fixed-point values
+ >>> b = Decimal('3.17')
+ >>> a + b # Addition preserves fixed-point
+ Decimal('105.89')
+ >>> a - b
+ Decimal('99.55')
+ >>> a * 42 # So does integer multiplication
+ Decimal('4314.24')
+ >>> (a * b).quantize(TWOPLACES) # Must quantize non-integer multiplication
+ Decimal('325.62')
+ >>> (b / a).quantize(TWOPLACES) # And quantize division
+ Decimal('0.03')
+
+In developing fixed-point applications, it is convenient to define functions
+to handle the :meth:`quantize` step::
+
+ >>> def mul(x, y, fp=TWOPLACES):
+ ... return (x * y).quantize(fp)
+ >>> def div(x, y, fp=TWOPLACES):
+ ... return (x / y).quantize(fp)
+
+ >>> mul(a, b) # Automatically preserve fixed-point
+ Decimal('325.62')
+ >>> div(b, a)
+ Decimal('0.03')
Q. There are many ways to express the same value. The numbers :const:`200`,
:const:`200.000`, :const:`2E2`, and :const:`.02E+4` all have the same value at
@@ -1537,6 +1556,16 @@ of significant places in the coefficient. For example, expressing
:const:`5.0E+3` as :const:`5000` keeps the value constant but cannot show the
original's two-place significance.
+If an application does not care about tracking significance, it is easy to
+remove the exponent and trailing zeroes, losing signficance, but keeping the
+value unchanged::
+
+ >>> def remove_exponent(d):
+ ... return d.quantize(Decimal(1)) if d == d.to_integral() else d.normalize()
+
+ >>> remove_exponent(Decimal('5E+3'))
+ Decimal('5000')
+
Q. Is there a way to convert a regular float to a :class:`Decimal`?
A. Yes, all binary floating point numbers can be exactly expressed as a