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author | Christian Heimes <christian@cheimes.de> | 2008-02-16 07:38:31 (GMT) |
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committer | Christian Heimes <christian@cheimes.de> | 2008-02-16 07:38:31 (GMT) |
commit | a156e09b19cd239176a9316ddca7641784eea99e (patch) | |
tree | 0aa8388d9496bbc7a0425f317007ab69e8049c70 /Doc/library | |
parent | 71316b0378d57a8ffe9733339318c8bdaccb706b (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
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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.
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r60791 | raymond.hettinger | 2008-02-14 11:46:57 +0100 (Thu, 14 Feb 2008) | 1 line
Add fixed-point examples to the decimal FAQ
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r60792 | raymond.hettinger | 2008-02-14 12:01:10 +0100 (Thu, 14 Feb 2008) | 1 line
Improve rst markup
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r60794 | raymond.hettinger | 2008-02-14 12:57:25 +0100 (Thu, 14 Feb 2008) | 1 line
Show how to remove exponents.
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r60795 | raymond.hettinger | 2008-02-14 13:05:42 +0100 (Thu, 14 Feb 2008) | 1 line
Fix markup.
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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.
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r60798 | raymond.hettinger | 2008-02-14 13:49:37 +0100 (Thu, 14 Feb 2008) | 1 line
Simplify moneyfmt() recipe.
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r60810 | raymond.hettinger | 2008-02-14 20:02:39 +0100 (Thu, 14 Feb 2008) | 1 line
Fix markup
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r60811 | raymond.hettinger | 2008-02-14 20:30:30 +0100 (Thu, 14 Feb 2008) | 1 line
No need to register subclass of ABCs.
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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.
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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
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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.
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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.
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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.
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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).
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r60840 | raymond.hettinger | 2008-02-15 22:21:25 +0100 (Fri, 15 Feb 2008) | 1 line
Update example to match the current syntax.
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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
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r60842 | amaury.forgeotdarc | 2008-02-15 22:27:44 +0100 (Fri, 15 Feb 2008) | 2 lines
Temporarily let these tests pass
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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.
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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.
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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.
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Diffstat (limited to 'Doc/library')
-rw-r--r-- | Doc/library/ctypes.rst | 1 | ||||
-rw-r--r-- | Doc/library/decimal.rst | 63 |
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 |