[Python-checkins] r79213 - in python/branches/release26-maint: Doc/c-api/buffer.rst Doc/c-api/init.rst Doc/faq/design.rst Doc/faq/programming.rst Doc/library/collections.rst Doc/library/functions.rst Doc/library/optparse.rst Doc/library/os.rst Doc/library/stdtypes.rst Doc/library/string.rst Doc/library/subprocess.rst Lib/subprocess.py
georg.brandl
python-checkins at python.org
Sun Mar 21 20:06:52 CET 2010
Author: georg.brandl
Date: Sun Mar 21 20:06:51 2010
New Revision: 79213
Log:
Merged revisions 76538,76559,76882-76883,76886,76891-76892,76920,76924-76925,77081,77084,77086,77092 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
........
r76538 | georg.brandl | 2009-11-26 21:48:25 +0100 (Do, 26 Nov 2009) | 1 line
#7400: typo.
........
r76559 | georg.brandl | 2009-11-28 12:11:50 +0100 (Sa, 28 Nov 2009) | 1 line
Fix versions and spacing.
........
r76882 | georg.brandl | 2009-12-19 18:30:28 +0100 (Sa, 19 Dez 2009) | 1 line
#7527: use standard versionadded tags.
........
r76883 | georg.brandl | 2009-12-19 18:34:32 +0100 (Sa, 19 Dez 2009) | 1 line
#7521: remove Py_GetBuildNumber(), which was removed in favor of Py_GetBuildInfo().
........
r76886 | georg.brandl | 2009-12-19 18:43:33 +0100 (Sa, 19 Dez 2009) | 1 line
#7493: review of Design FAQ by Florent Xicluna.
........
r76891 | georg.brandl | 2009-12-19 19:16:31 +0100 (Sa, 19 Dez 2009) | 1 line
#7479: add note about function availability on Unices.
........
r76892 | georg.brandl | 2009-12-19 19:20:18 +0100 (Sa, 19 Dez 2009) | 1 line
#7480: remove tautology.
........
r76920 | georg.brandl | 2009-12-20 15:20:16 +0100 (So, 20 Dez 2009) | 1 line
#7495: backport Programming FAQ review to trunk.
........
r76924 | georg.brandl | 2009-12-20 15:28:05 +0100 (So, 20 Dez 2009) | 1 line
Small indentation fix.
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r76925 | georg.brandl | 2009-12-20 15:33:20 +0100 (So, 20 Dez 2009) | 1 line
#7381: subprocess documentation and library docstring consistency fixes.
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r77081 | georg.brandl | 2009-12-28 08:59:05 +0100 (Mo, 28 Dez 2009) | 1 line
#7577: fix signature of PyBuffer_FillInfo().
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r77084 | georg.brandl | 2009-12-28 09:01:59 +0100 (Mo, 28 Dez 2009) | 1 line
#7586: fix typo.
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r77086 | georg.brandl | 2009-12-28 09:09:32 +0100 (Mo, 28 Dez 2009) | 1 line
#7381: consistency update, and backport avoiding ``None >= 0`` check from py3k.
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r77092 | georg.brandl | 2009-12-28 09:48:24 +0100 (Mo, 28 Dez 2009) | 1 line
#7404: remove reference to non-existing example files.
........
Modified:
python/branches/release26-maint/ (props changed)
python/branches/release26-maint/Doc/c-api/buffer.rst
python/branches/release26-maint/Doc/c-api/init.rst
python/branches/release26-maint/Doc/faq/design.rst
python/branches/release26-maint/Doc/faq/programming.rst
python/branches/release26-maint/Doc/library/collections.rst
python/branches/release26-maint/Doc/library/functions.rst
python/branches/release26-maint/Doc/library/optparse.rst
python/branches/release26-maint/Doc/library/os.rst
python/branches/release26-maint/Doc/library/stdtypes.rst
python/branches/release26-maint/Doc/library/string.rst
python/branches/release26-maint/Doc/library/subprocess.rst
python/branches/release26-maint/Lib/subprocess.py
Modified: python/branches/release26-maint/Doc/c-api/buffer.rst
==============================================================================
--- python/branches/release26-maint/Doc/c-api/buffer.rst (original)
+++ python/branches/release26-maint/Doc/c-api/buffer.rst Sun Mar 21 20:06:51 2010
@@ -293,7 +293,7 @@
given shape with the given number of bytes per element.
-.. cfunction:: int PyBuffer_FillInfo(Py_buffer *view, void *buf, Py_ssize_t len, int readonly, int infoflags)
+.. cfunction:: int PyBuffer_FillInfo(Py_buffer *view, PyObject *obj, void *buf, Py_ssize_t len, int readonly, int infoflags)
Fill in a buffer-info structure, *view*, correctly for an exporter that can
only share a contiguous chunk of memory of "unsigned bytes" of the given
Modified: python/branches/release26-maint/Doc/c-api/init.rst
==============================================================================
--- python/branches/release26-maint/Doc/c-api/init.rst (original)
+++ python/branches/release26-maint/Doc/c-api/init.rst Sun Mar 21 20:06:51 2010
@@ -284,15 +284,6 @@
modify its value. The value is available to Python code as ``sys.version``.
-.. cfunction:: const char* Py_GetBuildNumber()
-
- Return a string representing the Subversion revision that this Python executable
- was built from. This number is a string because it may contain a trailing 'M'
- if Python was built from a mixed revision source tree.
-
- .. versionadded:: 2.5
-
-
.. cfunction:: const char* Py_GetPlatform()
.. index:: single: platform (in module sys)
Modified: python/branches/release26-maint/Doc/faq/design.rst
==============================================================================
--- python/branches/release26-maint/Doc/faq/design.rst (original)
+++ python/branches/release26-maint/Doc/faq/design.rst Sun Mar 21 20:06:51 2010
@@ -7,7 +7,7 @@
Guido van Rossum believes that using indentation for grouping is extremely
elegant and contributes a lot to the clarity of the average Python program.
-Most people learn to love this feature after awhile.
+Most people learn to love this feature after a while.
Since there are no begin/end brackets there cannot be a disagreement between
grouping perceived by the parser and the human reader. Occasionally C
@@ -48,7 +48,7 @@
People are often very surprised by results like this::
- >>> 1.2-1.0
+ >>> 1.2 - 1.0
0.199999999999999996
and think it is a bug in Python. It's not. This has nothing to do with Python,
@@ -85,7 +85,7 @@
``==`` fails. Instead, you have to check that the difference between the two
numbers is less than a certain threshold::
- epsilon = 0.0000000000001 # Tiny allowed error
+ epsilon = 0.0000000000001 # Tiny allowed error
expected_result = 0.4
if expected_result-epsilon <= computation() <= expected_result+epsilon:
@@ -131,24 +131,25 @@
Second, it means that no special syntax is necessary if you want to explicitly
reference or call the method from a particular class. In C++, if you want to
use a method from a base class which is overridden in a derived class, you have
-to use the ``::`` operator -- in Python you can write baseclass.methodname(self,
-<argument list>). This is particularly useful for :meth:`__init__` methods, and
-in general in cases where a derived class method wants to extend the base class
-method of the same name and thus has to call the base class method somehow.
+to use the ``::`` operator -- in Python you can write
+``baseclass.methodname(self, <argument list>)``. This is particularly useful
+for :meth:`__init__` methods, and in general in cases where a derived class
+method wants to extend the base class method of the same name and thus has to
+call the base class method somehow.
Finally, for instance variables it solves a syntactic problem with assignment:
since local variables in Python are (by definition!) those variables to which a
-value assigned in a function body (and that aren't explicitly declared global),
-there has to be some way to tell the interpreter that an assignment was meant to
-assign to an instance variable instead of to a local variable, and it should
-preferably be syntactic (for efficiency reasons). C++ does this through
+value is assigned in a function body (and that aren't explicitly declared
+global), there has to be some way to tell the interpreter that an assignment was
+meant to assign to an instance variable instead of to a local variable, and it
+should preferably be syntactic (for efficiency reasons). C++ does this through
declarations, but Python doesn't have declarations and it would be a pity having
-to introduce them just for this purpose. Using the explicit "self.var" solves
+to introduce them just for this purpose. Using the explicit ``self.var`` solves
this nicely. Similarly, for using instance variables, having to write
-"self.var" means that references to unqualified names inside a method don't have
-to search the instance's directories. To put it another way, local variables
-and instance variables live in two different namespaces, and you need to tell
-Python which namespace to use.
+``self.var`` means that references to unqualified names inside a method don't
+have to search the instance's directories. To put it another way, local
+variables and instance variables live in two different namespaces, and you need
+to tell Python which namespace to use.
Why can't I use an assignment in an expression?
@@ -234,8 +235,10 @@
.. XXX talk about protocols?
-Note that for string operations Python has moved from external functions (the
-``string`` module) to methods. However, ``len()`` is still a function.
+.. note::
+
+ For string operations, Python has moved from external functions (the
+ ``string`` module) to methods. However, ``len()`` is still a function.
Why is join() a string method instead of a list or tuple method?
@@ -298,22 +301,24 @@
expensive. In versions of Python prior to 2.0 it was common to use this idiom::
try:
- value = dict[key]
+ value = mydict[key]
except KeyError:
- dict[key] = getvalue(key)
- value = dict[key]
+ mydict[key] = getvalue(key)
+ value = mydict[key]
This only made sense when you expected the dict to have the key almost all the
time. If that wasn't the case, you coded it like this::
- if dict.has_key(key):
- value = dict[key]
+ if mydict.has_key(key):
+ value = mydict[key]
else:
- dict[key] = getvalue(key)
- value = dict[key]
+ mydict[key] = getvalue(key)
+ value = mydict[key]
+
+.. note::
-(In Python 2.0 and higher, you can code this as ``value = dict.setdefault(key,
-getvalue(key))``.)
+ In Python 2.0 and higher, you can code this as ``value =
+ mydict.setdefault(key, getvalue(key))``.
Why isn't there a switch or case statement in Python?
@@ -432,7 +437,7 @@
<http://www.cosc.canterbury.ac.nz/~greg/python/Pyrex/>`_, `PyInline
<http://pyinline.sourceforge.net/>`_, `Py2Cmod
<http://sourceforge.net/projects/py2cmod/>`_, and `Weave
-<http://www.scipy.org/site_content/weave>`_.
+<http://www.scipy.org/Weave>`_.
How does Python manage memory?
@@ -450,6 +455,8 @@
difference can cause some subtle porting problems if your Python code depends on
the behavior of the reference counting implementation.
+.. XXX relevant for Python 2.6?
+
Sometimes objects get stuck in tracebacks temporarily and hence are not
deallocated when you might expect. Clear the tracebacks with::
@@ -461,8 +468,8 @@
things. They contain a portion of the program state extracted during the
handling of an exception (usually the most recent exception).
-In the absence of circularities and tracebacks, Python programs need not
-explicitly manage memory.
+In the absence of circularities and tracebacks, Python programs do not need to
+manage memory explicitly.
Why doesn't Python use a more traditional garbage collection scheme? For one
thing, this is not a C standard feature and hence it's not portable. (Yes, we
@@ -481,19 +488,19 @@
In Jython, the following code (which is fine in CPython) will probably run out
of file descriptors long before it runs out of memory::
- for file in <very long list of files>:
+ for file in very_long_list_of_files:
f = open(file)
c = f.read(1)
Using the current reference counting and destructor scheme, each new assignment
to f closes the previous file. Using GC, this is not guaranteed. If you want
to write code that will work with any Python implementation, you should
-explicitly close the file; this will work regardless of GC::
+explicitly close the file or use the :keyword:`with` statement; this will work
+regardless of GC::
- for file in <very long list of files>:
- f = open(file)
- c = f.read(1)
- f.close()
+ for file in very_long_list_of_files:
+ with open(file) as f:
+ c = f.read(1)
Why isn't all memory freed when Python exits?
@@ -589,10 +596,10 @@
- Hash lists by their address (object ID). This doesn't work because if you
construct a new list with the same value it won't be found; e.g.::
- d = {[1,2]: '12'}
- print d[[1,2]]
+ mydict = {[1, 2]: '12'}
+ print mydict[[1, 2]]
- would raise a KeyError exception because the id of the ``[1,2]`` used in the
+ would raise a KeyError exception because the id of the ``[1, 2]`` used in the
second line differs from that in the first line. In other words, dictionary
keys should be compared using ``==``, not using :keyword:`is`.
@@ -613,7 +620,7 @@
There is a trick to get around this if you need to, but use it at your own risk:
You can wrap a mutable structure inside a class instance which has both a
-:meth:`__cmp_` and a :meth:`__hash__` method. You must then make sure that the
+:meth:`__eq__` and a :meth:`__hash__` method. You must then make sure that the
hash value for all such wrapper objects that reside in a dictionary (or other
hash based structure), remain fixed while the object is in the dictionary (or
other structure). ::
@@ -621,15 +628,15 @@
class ListWrapper:
def __init__(self, the_list):
self.the_list = the_list
- def __cmp__(self, other):
+ def __eq__(self, other):
return self.the_list == other.the_list
def __hash__(self):
l = self.the_list
result = 98767 - len(l)*555
- for i in range(len(l)):
+ for i, el in enumerate(l):
try:
- result = result + (hash(l[i]) % 9999999) * 1001 + i
- except:
+ result = result + (hash(el) % 9999999) * 1001 + i
+ except Exception:
result = (result % 7777777) + i * 333
return result
@@ -637,8 +644,8 @@
members of the list may be unhashable and also by the possibility of arithmetic
overflow.
-Furthermore it must always be the case that if ``o1 == o2`` (ie ``o1.__cmp__(o2)
-== 0``) then ``hash(o1) == hash(o2)`` (ie, ``o1.__hash__() == o2.__hash__()``),
+Furthermore it must always be the case that if ``o1 == o2`` (ie ``o1.__eq__(o2)
+is True``) then ``hash(o1) == hash(o2)`` (ie, ``o1.__hash__() == o2.__hash__()``),
regardless of whether the object is in a dictionary or not. If you fail to meet
these restrictions dictionaries and other hash based structures will misbehave.
@@ -662,8 +669,8 @@
it. For example, here's how to iterate over the keys of a dictionary in sorted
order::
- for key in sorted(dict.iterkeys()):
- ... # do whatever with dict[key]...
+ for key in sorted(mydict):
+ ... # do whatever with mydict[key]...
How do you specify and enforce an interface spec in Python?
@@ -712,14 +719,14 @@
This type of bug commonly bites neophyte programmers. Consider this function::
- def foo(D={}): # Danger: shared reference to one dict for all calls
+ def foo(mydict={}): # Danger: shared reference to one dict for all calls
... compute something ...
- D[key] = value
- return D
+ mydict[key] = value
+ return mydict
-The first time you call this function, ``D`` contains a single item. The second
-time, ``D`` contains two items because when ``foo()`` begins executing, ``D``
-starts out with an item already in it.
+The first time you call this function, ``mydict`` contains a single item. The
+second time, ``mydict`` contains two items because when ``foo()`` begins
+executing, ``mydict`` starts out with an item already in it.
It is often expected that a function call creates new objects for default
values. This is not what happens. Default values are created exactly once, when
@@ -735,14 +742,14 @@
inside the function, check if the parameter is ``None`` and create a new
list/dictionary/whatever if it is. For example, don't write::
- def foo(dict={}):
+ def foo(mydict={}):
...
but::
- def foo(dict=None):
- if dict is None:
- dict = {} # create a new dict for local namespace
+ def foo(mydict=None):
+ if mydict is None:
+ mydict = {} # create a new dict for local namespace
This feature can be useful. When you have a function that's time-consuming to
compute, a common technique is to cache the parameters and the resulting value
@@ -751,7 +758,7 @@
# Callers will never provide a third parameter for this function.
def expensive (arg1, arg2, _cache={}):
- if _cache.has_key((arg1, arg2)):
+ if (arg1, arg2) in _cache:
return _cache[(arg1, arg2)]
# Calculate the value
@@ -771,13 +778,13 @@
reasonable uses of the "go" or "goto" constructs of C, Fortran, and other
languages. For example::
- class label: pass # declare a label
+ class label: pass # declare a label
try:
...
- if (condition): raise label() # goto label
+ if (condition): raise label() # goto label
...
- except label: # where to goto
+ except label: # where to goto
pass
...
@@ -802,7 +809,7 @@
If you're trying to build Windows pathnames, note that all Windows system calls
accept forward slashes too::
- f = open("/mydir/file.txt") # works fine!
+ f = open("/mydir/file.txt") # works fine!
If you're trying to build a pathname for a DOS command, try e.g. one of ::
@@ -819,7 +826,7 @@
looks like this::
with obj:
- a = 1 # equivalent to obj.a = 1
+ a = 1 # equivalent to obj.a = 1
total = total + 1 # obj.total = obj.total + 1
In Python, such a construct would be ambiguous.
@@ -850,21 +857,20 @@
The primary benefit of "with" and similar language features (reduction of code
volume) can, however, easily be achieved in Python by assignment. Instead of::
- function(args).dict[index][index].a = 21
- function(args).dict[index][index].b = 42
- function(args).dict[index][index].c = 63
+ function(args).mydict[index][index].a = 21
+ function(args).mydict[index][index].b = 42
+ function(args).mydict[index][index].c = 63
write this::
- ref = function(args).dict[index][index]
+ ref = function(args).mydict[index][index]
ref.a = 21
ref.b = 42
ref.c = 63
This also has the side-effect of increasing execution speed because name
bindings are resolved at run-time in Python, and the second version only needs
-to perform the resolution once. If the referenced object does not have a, b and
-c attributes, of course, the end result is still a run-time exception.
+to perform the resolution once.
Why are colons required for the if/while/def/class statements?
Modified: python/branches/release26-maint/Doc/faq/programming.rst
==============================================================================
--- python/branches/release26-maint/Doc/faq/programming.rst (original)
+++ python/branches/release26-maint/Doc/faq/programming.rst Sun Mar 21 20:06:51 2010
@@ -176,32 +176,33 @@
it is much shorter and far faster to use ::
- L2 = list(L1[:3]) # "list" is redundant if L1 is a list.
+ L2 = list(L1[:3]) # "list" is redundant if L1 is a list.
Note that the functionally-oriented built-in functions such as :func:`map`,
:func:`zip`, and friends can be a convenient accelerator for loops that
perform a single task. For example to pair the elements of two lists
together::
- >>> zip([1,2,3], [4,5,6])
+ >>> zip([1, 2, 3], [4, 5, 6])
[(1, 4), (2, 5), (3, 6)]
or to compute a number of sines::
- >>> map( math.sin, (1,2,3,4))
- [0.841470984808, 0.909297426826, 0.14112000806, -0.756802495308]
+ >>> map(math.sin, (1, 2, 3, 4))
+ [0.841470984808, 0.909297426826, 0.14112000806, -0.756802495308]
The operation completes very quickly in such cases.
-Other examples include the ``join()`` and ``split()`` methods of string objects.
+Other examples include the ``join()`` and ``split()`` :ref:`methods
+of string objects <string-methods>`.
For example if s1..s7 are large (10K+) strings then
``"".join([s1,s2,s3,s4,s5,s6,s7])`` may be far faster than the more obvious
``s1+s2+s3+s4+s5+s6+s7``, since the "summation" will compute many
subexpressions, whereas ``join()`` does all the copying in one pass. For
-manipulating strings, use the ``replace()`` method on string objects. Use
-regular expressions only when you're not dealing with constant string patterns.
-Consider using the string formatting operations ``string % tuple`` and ``string
-% dictionary``.
+manipulating strings, use the ``replace()`` and the ``format()`` :ref:`methods
+on string objects <string-methods>`. Use regular expressions only when you're
+not dealing with constant string patterns. You may still use :ref:`the old %
+operations <string-formatting>` ``string % tuple`` and ``string % dictionary``.
Be sure to use the :meth:`list.sort` built-in method to do sorting, and see the
`sorting mini-HOWTO <http://wiki.python.org/moin/HowTo/Sorting>`_ for examples
@@ -211,7 +212,7 @@
Another common trick is to "push loops into functions or methods." For example
suppose you have a program that runs slowly and you use the profiler to
determine that a Python function ``ff()`` is being called lots of times. If you
-notice that ``ff ()``::
+notice that ``ff()``::
def ff(x):
... # do something with x computing result...
@@ -332,24 +333,6 @@
>>> print x
11
-In Python3, you can do a similar thing in a nested scope using the
-:keyword:`nonlocal` keyword:
-
-.. doctest::
- :options: +SKIP
-
- >>> def foo():
- ... x = 10
- ... def bar():
- ... nonlocal x
- ... print x
- ... x += 1
- ... bar()
- ... print x
- >>> foo()
- 10
- 11
-
What are the rules for local and global variables in Python?
------------------------------------------------------------
@@ -412,7 +395,7 @@
It's good practice if you import modules in the following order:
-1. standard library modules -- e.g. ``sys``, ``os``, ``getopt``, ``re``)
+1. standard library modules -- e.g. ``sys``, ``os``, ``getopt``, ``re``
2. third-party library modules (anything installed in Python's site-packages
directory) -- e.g. mx.DateTime, ZODB, PIL.Image, etc.
3. locally-developed modules
@@ -421,7 +404,7 @@
``package.sub.m1`` module and want to import ``package.sub.m2``, do not just
write ``import m2``, even though it's legal. Write ``from package.sub import
m2`` instead. Relative imports can lead to a module being initialized twice,
-leading to confusing bugs.
+leading to confusing bugs. See :pep:`328` for details.
It is sometimes necessary to move imports to a function or class to avoid
problems with circular imports. Gordon McMillan says:
@@ -649,9 +632,9 @@
a = B()
b = a
print b
- <__main__.A instance at 016D07CC>
+ <__main__.A instance at 0x16D07CC>
print a
- <__main__.A instance at 016D07CC>
+ <__main__.A instance at 0x16D07CC>
Arguably the class has a name: even though it is bound to two names and invoked
through the name B the created instance is still reported as an instance of
@@ -681,7 +664,7 @@
Comma is not an operator in Python. Consider this session::
>>> "a" in "b", "a"
- (False, '1')
+ (False, 'a')
Since the comma is not an operator, but a separator between expressions the
above is evaluated as if you had entered::
@@ -690,7 +673,7 @@
not::
- >>> "a" in ("5", "a")
+ >>> "a" in ("b", "a")
The same is true of the various assignment operators (``=``, ``+=`` etc). They
are not truly operators but syntactic delimiters in assignment statements.
@@ -732,12 +715,12 @@
if not isfunction(on_true):
return on_true
else:
- return apply(on_true)
+ return on_true()
else:
if not isfunction(on_false):
return on_false
else:
- return apply(on_false)
+ return on_false()
In most cases you'll pass b and c directly: ``q(a, b, c)``. To avoid evaluating
b or c when they shouldn't be, encapsulate them within a lambda function, e.g.:
@@ -767,7 +750,7 @@
map(lambda x,y=y:y%x,range(2,int(pow(y,0.5)+1))),1),range(2,1000)))
# First 10 Fibonacci numbers
- print map(lambda x,f=lambda x,f:(x<=1) or (f(x-1,f)+f(x-2,f)): f(x,f),
+ print map(lambda x,f=lambda x,f:(f(x-1,f)+f(x-2,f)) if x>1 else 1: f(x,f),
range(10))
# Mandelbrot set
@@ -793,10 +776,11 @@
How do I specify hexadecimal and octal integers?
------------------------------------------------
-To specify an octal digit, precede the octal value with a zero. For example, to
-set the variable "a" to the octal value "10" (8 in decimal), type::
+To specify an octal digit, precede the octal value with a zero, and then a lower
+or uppercase "o". For example, to set the variable "a" to the octal value "10"
+(8 in decimal), type::
- >>> a = 010
+ >>> a = 0o10
>>> a
8
@@ -812,17 +796,17 @@
178
-Why does -22 / 10 return -3?
-----------------------------
+Why does -22 // 10 return -3?
+-----------------------------
It's primarily driven by the desire that ``i % j`` have the same sign as ``j``.
If you want that, and also want::
- i == (i / j) * j + (i % j)
+ i == (i // j) * j + (i % j)
then integer division has to return the floor. C also requires that identity to
-hold, and then compilers that truncate ``i / j`` need to make ``i % j`` have the
-same sign as ``i``.
+hold, and then compilers that truncate ``i // j`` need to make ``i % j`` have
+the same sign as ``i``.
There are few real use cases for ``i % j`` when ``j`` is negative. When ``j``
is positive, there are many, and in virtually all of them it's more useful for
@@ -830,6 +814,12 @@
ago? ``-190 % 12 == 2`` is useful; ``-190 % 12 == -10`` is a bug waiting to
bite.
+.. note::
+
+ On Python 2, ``a / b`` returns the same as ``a // b`` if
+ ``__future__.division`` is not in effect. This is also known as "classic"
+ division.
+
How do I convert a string to a number?
--------------------------------------
@@ -861,10 +851,11 @@
To convert, e.g., the number 144 to the string '144', use the built-in type
constructor :func:`str`. If you want a hexadecimal or octal representation, use
-the built-in functions ``hex()`` or ``oct()``. For fancy formatting, use
-:ref:`the % operator <string-formatting>` on strings, e.g. ``"%04d" % 144``
-yields ``'0144'`` and ``"%.3f" % (1/3.0)`` yields ``'0.333'``. See the library
-reference manual for details.
+the built-in functions :func:`hex` or :func:`oct`. For fancy formatting, see
+the :ref:`formatstrings` section, e.g. ``"{:04d}".format(144)`` yields
+``'0144'`` and ``"{:.3f}".format(1/3)`` yields ``'0.333'``. You may also use
+:ref:`the % operator <string-formatting>` on strings. See the library reference
+manual for details.
How do I modify a string in place?
@@ -962,12 +953,12 @@
... "\r\n"
... "\r\n")
>>> lines.rstrip("\n\r")
- "line 1 "
+ 'line 1 '
Since this is typically only desired when reading text one line at a time, using
``S.rstrip()`` this way works well.
-For older versions of Python, There are two partial substitutes:
+For older versions of Python, there are two partial substitutes:
- If you want to remove all trailing whitespace, use the ``rstrip()`` method of
string objects. This removes all trailing whitespace, not just a single
@@ -1093,26 +1084,26 @@
If you don't mind reordering the list, sort it and then scan from the end of the
list, deleting duplicates as you go::
- if List:
- List.sort()
- last = List[-1]
- for i in range(len(List)-2, -1, -1):
- if last == List[i]:
- del List[i]
+ if mylist:
+ mylist.sort()
+ last = mylist[-1]
+ for i in range(len(mylist)-2, -1, -1):
+ if last == mylist[i]:
+ del mylist[i]
else:
- last = List[i]
+ last = mylist[i]
If all elements of the list may be used as dictionary keys (i.e. they are all
hashable) this is often faster ::
d = {}
- for x in List:
- d[x] = x
- List = d.values()
+ for x in mylist:
+ d[x] = 1
+ mylist = list(d.keys())
In Python 2.5 and later, the following is possible instead::
- List = list(set(List))
+ mylist = list(set(mylist))
This converts the list into a set, thereby removing duplicates, and then back
into a list.
@@ -1188,7 +1179,7 @@
Use a list comprehension::
- result = [obj.method() for obj in List]
+ result = [obj.method() for obj in mylist]
More generically, you can try the following function::
@@ -1213,23 +1204,17 @@
case, use the ``pprint`` module to pretty-print the dictionary; the items will
be presented in order sorted by the key.
-A more complicated solution is to subclass ``UserDict.UserDict`` to create a
+A more complicated solution is to subclass ``dict`` to create a
``SortedDict`` class that prints itself in a predictable order. Here's one
simpleminded implementation of such a class::
- import UserDict, string
-
- class SortedDict(UserDict.UserDict):
+ class SortedDict(dict):
def __repr__(self):
- result = []
- append = result.append
- keys = self.data.keys()
- keys.sort()
- for k in keys:
- append("%s: %s" % (`k`, `self.data[k]`))
- return "{%s}" % string.join(result, ", ")
+ keys = sorted(self.keys())
+ result = ("{!r}: {!r}".format(k, self[k]) for k in keys)
+ return "{{{}}}".format(", ".join(result))
- __str__ = __repr__
+ __str__ = __repr__
This will work for many common situations you might encounter, though it's far
from a perfect solution. The largest flaw is that if some values in the
@@ -1251,14 +1236,14 @@
sorting is quite simple to do with list comprehensions. To sort a list of
strings by their uppercase values::
- tmp1 = [(x.upper(), x) for x in L] # Schwartzian transform
+ tmp1 = [(x.upper(), x) for x in L] # Schwartzian transform
tmp1.sort()
Usorted = [x[1] for x in tmp1]
To sort by the integer value of a subfield extending from positions 10-15 in
each string::
- tmp2 = [(int(s[10:15]), s) for s in L] # Schwartzian transform
+ tmp2 = [(int(s[10:15]), s) for s in L] # Schwartzian transform
tmp2.sort()
Isorted = [x[1] for x in tmp2]
@@ -1295,8 +1280,8 @@
An alternative for the last step is::
- result = []
- for p in pairs: result.append(p[1])
+ >>> result = []
+ >>> for p in pairs: result.append(p[1])
If you find this more legible, you might prefer to use this instead of the final
list comprehension. However, it is almost twice as slow for long lists. Why?
@@ -1364,7 +1349,7 @@
different thing based on what class it is. For example, if you have a function
that does something::
- def search (obj):
+ def search(obj):
if isinstance(obj, Mailbox):
# ... code to search a mailbox
elif isinstance(obj, Document):
@@ -1467,8 +1452,8 @@
How do I create static class data and static class methods?
-----------------------------------------------------------
-Static data (in the sense of C++ or Java) is easy; static methods (again in the
-sense of C++ or Java) are not supported directly.
+Both static data and static methods (in the sense of C++ or Java) are supported
+in Python.
For static data, simply define a class attribute. To assign a new value to the
attribute, you have to explicitly use the class name in the assignment::
@@ -1487,9 +1472,9 @@
search path from ``c.__class__`` back to ``C``.
Caution: within a method of C, an assignment like ``self.count = 42`` creates a
-new and unrelated instance vrbl named "count" in ``self``'s own dict. Rebinding
-of a class-static data name must always specify the class whether inside a
-method or not::
+new and unrelated instance named "count" in ``self``'s own dict. Rebinding of a
+class-static data name must always specify the class whether inside a method or
+not::
C.count = 314
Modified: python/branches/release26-maint/Doc/library/collections.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/collections.rst (original)
+++ python/branches/release26-maint/Doc/library/collections.rst Sun Mar 21 20:06:51 2010
@@ -650,7 +650,7 @@
Point: x= 3.000 y= 4.000 hypot= 5.000
Point: x=14.000 y= 0.714 hypot=14.018
-The subclass shown above sets ``__slots__`` to an empty tuple. This keeps
+The subclass shown above sets ``__slots__`` to an empty tuple. This helps
keep memory requirements low by preventing the creation of instance dictionaries.
Subclassing is not useful for adding new, stored fields. Instead, simply
Modified: python/branches/release26-maint/Doc/library/functions.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/functions.rst (original)
+++ python/branches/release26-maint/Doc/library/functions.rst Sun Mar 21 20:06:51 2010
@@ -1087,7 +1087,7 @@
.. function:: set([iterable])
:noindex:
- Return a new set, optionally with elements are taken from *iterable*.
+ Return a new set, optionally with elements taken from *iterable*.
The set type is described in :ref:`types-set`.
For other containers see the built in :class:`dict`, :class:`list`, and
Modified: python/branches/release26-maint/Doc/library/optparse.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/optparse.rst (original)
+++ python/branches/release26-maint/Doc/library/optparse.rst Sun Mar 21 20:06:51 2010
@@ -163,9 +163,7 @@
an option that must be supplied on the command-line; note that the phrase
"required option" is self-contradictory in English. :mod:`optparse` doesn't
prevent you from implementing required options, but doesn't give you much
- help at it either. See ``examples/required_1.py`` and
- ``examples/required_2.py`` in the :mod:`optparse` source distribution for two
- ways to implement required options with :mod:`optparse`.
+ help at it either.
For example, consider this hypothetical command-line::
Modified: python/branches/release26-maint/Doc/library/os.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/os.rst (original)
+++ python/branches/release26-maint/Doc/library/os.rst Sun Mar 21 20:06:51 2010
@@ -13,19 +13,24 @@
module, and for high-level file and directory handling see the :mod:`shutil`
module.
-The design of all built-in operating system dependent modules of Python is such
-that as long as the same functionality is available, it uses the same interface;
-for example, the function ``os.stat(path)`` returns stat information about
-*path* in the same format (which happens to have originated with the POSIX
-interface).
+Notes on the availability of these functions:
-Extensions peculiar to a particular operating system are also available through
-the :mod:`os` module, but using them is of course a threat to portability!
+* The design of all built-in operating system dependent modules of Python is
+ such that as long as the same functionality is available, it uses the same
+ interface; for example, the function ``os.stat(path)`` returns stat
+ information about *path* in the same format (which happens to have originated
+ with the POSIX interface).
+
+* Extensions peculiar to a particular operating system are also available
+ through the :mod:`os` module, but using them is of course a threat to
+ portability.
+
+* An "Availability: Unix" note means that this function is commonly found on
+ Unix systems. It does not make any claims about its existence on a specific
+ operating system.
-.. note::
-
- If not separately noted, all functions that claim "Availability: Unix" are
- supported on Mac OS X, which builds on a Unix core.
+* If not separately noted, all functions that claim "Availability: Unix" are
+ supported on Mac OS X, which builds on a Unix core.
.. note::
@@ -41,9 +46,9 @@
.. data:: name
- The name of the operating system dependent module imported. The following names
- have currently been registered: ``'posix'``, ``'nt'``, ``'mac'``, ``'os2'``,
- ``'ce'``, ``'java'``, ``'riscos'``.
+ The name of the operating system dependent module imported. The following
+ names have currently been registered: ``'posix'``, ``'nt'``, ``'mac'``,
+ ``'os2'``, ``'ce'``, ``'java'``, ``'riscos'``.
.. _os-procinfo:
Modified: python/branches/release26-maint/Doc/library/stdtypes.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/stdtypes.rst (original)
+++ python/branches/release26-maint/Doc/library/stdtypes.rst Sun Mar 21 20:06:51 2010
@@ -2695,8 +2695,7 @@
.. attribute:: class.__bases__
- The tuple of base classes of a class object. If there are no base classes, this
- will be an empty tuple.
+ The tuple of base classes of a class object.
.. attribute:: class.__name__
Modified: python/branches/release26-maint/Doc/library/string.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/string.rst (original)
+++ python/branches/release26-maint/Doc/library/string.rst Sun Mar 21 20:06:51 2010
@@ -105,7 +105,9 @@
String Formatting
-----------------
-Starting in Python 2.6, the built-in str and unicode classes provide the ability
+.. versionadded:: 2.6
+
+The built-in str and unicode classes provide the ability
to do complex variable substitutions and value formatting via the
:meth:`str.format` method described in :pep:`3101`. The :class:`Formatter`
class in the :mod:`string` module allows you to create and customize your own
@@ -495,6 +497,8 @@
Template strings
----------------
+.. versionadded:: 2.4
+
Templates provide simpler string substitutions as described in :pep:`292`.
Instead of the normal ``%``\ -based substitutions, Templates support ``$``\
-based substitutions, using the following rules:
@@ -513,8 +517,6 @@
Any other appearance of ``$`` in the string will result in a :exc:`ValueError`
being raised.
-.. versionadded:: 2.4
-
The :mod:`string` module provides a :class:`Template` class that implements
these rules. The methods of :class:`Template` are:
Modified: python/branches/release26-maint/Doc/library/subprocess.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/subprocess.rst (original)
+++ python/branches/release26-maint/Doc/library/subprocess.rst Sun Mar 21 20:06:51 2010
@@ -151,9 +151,10 @@
.. note::
- This feature is only available if Python is built with universal newline support
- (the default). Also, the newlines attribute of the file objects :attr:`stdout`,
- :attr:`stdin` and :attr:`stderr` are not updated by the communicate() method.
+ This feature is only available if Python is built with universal newline
+ support (the default). Also, the newlines attribute of the file objects
+ :attr:`stdout`, :attr:`stdin` and :attr:`stderr` are not updated by the
+ communicate() method.
The *startupinfo* and *creationflags*, if given, will be passed to the
underlying CreateProcess() function. They can specify things such as appearance
@@ -187,7 +188,7 @@
The arguments are the same as for the Popen constructor. Example::
- retcode = call(["ls", "-l"])
+ >>> retcode = subprocess.call(["ls", "-l"])
.. function:: check_call(*popenargs, **kwargs)
@@ -199,7 +200,8 @@
The arguments are the same as for the Popen constructor. Example::
- check_call(["ls", "-l"])
+ >>> subprocess.check_call(["ls", "-l"])
+ 0
.. versionadded:: 2.5
Modified: python/branches/release26-maint/Lib/subprocess.py
==============================================================================
--- python/branches/release26-maint/Lib/subprocess.py (original)
+++ python/branches/release26-maint/Lib/subprocess.py Sun Mar 21 20:06:51 2010
@@ -447,7 +447,8 @@
def _cleanup():
for inst in _active[:]:
- if inst._internal_poll(_deadstate=sys.maxint) >= 0:
+ res = inst._internal_poll(_deadstate=sys.maxint)
+ if res is not None and res >= 0:
try:
_active.remove(inst)
except ValueError:
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