[Python-3000-checkins] r63656 - in python/branches/py3k: Doc/tutorial/controlflow.rst Doc/tutorial/datastructures.rst Doc/tutorial/errors.rst Doc/tutorial/floatingpoint.rst Doc/tutorial/inputoutput.rst Doc/tutorial/introduction.rst Doc/tutorial/stdlib2.rst
benjamin.peterson
python-3000-checkins at python.org
Mon May 26 03:03:56 CEST 2008
Author: benjamin.peterson
Date: Mon May 26 03:03:56 2008
New Revision: 63656
Log:
Merged revisions 63655 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
........
r63655 | benjamin.peterson | 2008-05-25 19:54:22 -0500 (Sun, 25 May 2008) | 2 lines
update the tutorial to use str.format
........
Modified:
python/branches/py3k/ (props changed)
python/branches/py3k/Doc/tutorial/controlflow.rst
python/branches/py3k/Doc/tutorial/datastructures.rst
python/branches/py3k/Doc/tutorial/errors.rst
python/branches/py3k/Doc/tutorial/floatingpoint.rst
python/branches/py3k/Doc/tutorial/inputoutput.rst
python/branches/py3k/Doc/tutorial/introduction.rst
python/branches/py3k/Doc/tutorial/stdlib2.rst
Modified: python/branches/py3k/Doc/tutorial/controlflow.rst
==============================================================================
--- python/branches/py3k/Doc/tutorial/controlflow.rst (original)
+++ python/branches/py3k/Doc/tutorial/controlflow.rst Mon May 26 03:03:56 2008
@@ -475,8 +475,8 @@
up in a tuple. Before the variable number of arguments, zero or more normal
arguments may occur. ::
- def fprintf(file, format, *args):
- file.write(format % args)
+ def fprintf(file, template, *args):
+ file.write(template.format(args))
Normally, these ``variadic`` arguments will be last in the list of formal
Modified: python/branches/py3k/Doc/tutorial/datastructures.rst
==============================================================================
--- python/branches/py3k/Doc/tutorial/datastructures.rst (original)
+++ python/branches/py3k/Doc/tutorial/datastructures.rst Mon May 26 03:03:56 2008
@@ -515,7 +515,7 @@
>>> questions = ['name', 'quest', 'favorite color']
>>> answers = ['lancelot', 'the holy grail', 'blue']
>>> for q, a in zip(questions, answers):
- ... print('What is your %s? It is %s.' % (q, a))
+ ... print('What is your {0}? It is {1}.'.format(q, a))
...
What is your name? It is lancelot.
What is your quest? It is the holy grail.
Modified: python/branches/py3k/Doc/tutorial/errors.rst
==============================================================================
--- python/branches/py3k/Doc/tutorial/errors.rst (original)
+++ python/branches/py3k/Doc/tutorial/errors.rst Mon May 26 03:03:56 2008
@@ -132,7 +132,7 @@
s = f.readline()
i = int(s.strip())
except IOError as (errno, strerror):
- print("I/O error(%s): %s" % (errno, strerror))
+ print("I/O error({0}): {1}".format(errno, strerror))
except ValueError:
print("Could not convert data to an integer.")
except:
Modified: python/branches/py3k/Doc/tutorial/floatingpoint.rst
==============================================================================
--- python/branches/py3k/Doc/tutorial/floatingpoint.rst (original)
+++ python/branches/py3k/Doc/tutorial/floatingpoint.rst Mon May 26 03:03:56 2008
@@ -132,9 +132,8 @@
While pathological cases do exist, for most casual use of floating-point
arithmetic you'll see the result you expect in the end if you simply round the
display of your final results to the number of decimal digits you expect.
-:func:`str` usually suffices, and for finer control see the discussion of
-Python's ``%`` format operator: the ``%g``, ``%f`` and ``%e`` format codes
-supply flexible and easy ways to round float results for display.
+:func:`str` usually suffices, and for finer control see the :meth:`str.format`
+method's format specifiers in :ref:`formatstrings`.
If you are a heavy user of floating point operations you should take a look
at the Numerical Python package and many other packages for mathematical and
Modified: python/branches/py3k/Doc/tutorial/inputoutput.rst
==============================================================================
--- python/branches/py3k/Doc/tutorial/inputoutput.rst (original)
+++ python/branches/py3k/Doc/tutorial/inputoutput.rst Mon May 26 03:03:56 2008
@@ -27,16 +27,16 @@
concatenation operations you can create any layout you can imagine. The
standard module :mod:`string` contains some useful operations for padding
strings to a given column width; these will be discussed shortly. The second
-way is to use the ``%`` operator with a string as the left argument. The ``%``
-operator interprets the left argument much like a :cfunc:`sprintf`\ -style
-format string to be applied to the right argument, and returns the string
-resulting from this formatting operation.
+way is to use the :meth:`str.format` method.
+
+The :mod:`string` module contains a class Template which offers yet another way
+to substitute values into strings.
One question remains, of course: how do you convert values to strings? Luckily,
Python has ways to convert any value to a string: pass it to the :func:`repr`
or :func:`str` functions. Reverse quotes (``````) are equivalent to
-:func:`repr`, but they are no longer used in modern Python code and will likely
-not be in future versions of the language.
+:func:`repr`, but they are no longer used in modern Python code and are removed
+in future versions of the language.
The :func:`str` function is meant to return representations of values which are
fairly human-readable, while :func:`repr` is meant to generate representations
@@ -94,7 +94,7 @@
10 100 1000
>>> for x in range(1, 11):
- ... print('%2d %3d %4d' % (x, x*x, x*x*x))
+ ... print('{0:2d} {1:3d} {2:4d}'.format(x, x*x, x*x*x))
...
1 1 1
2 4 8
@@ -129,44 +129,91 @@
>>> '3.14159265359'.zfill(5)
'3.14159265359'
-Using the ``%`` operator looks like this::
+Basic usage of the :meth:`str.format` method looks like this::
+
+ >>> print 'We are the {0} who say "{1}!"'.format('knights', 'Ni')
+ We are the knights who say "Ni!"
+
+The brackets and characters within them (called format fields) are replaced with
+the objects passed into the format method. The number in the brackets refers to
+the position of the object passed into the format method. ::
+
+ >>> print '{0} and {1}'.format('spam', 'eggs')
+ spam and eggs
+ >>> print '{1} and {0}'.format('spam', 'eggs')
+ eggs and spam
+
+If keyword arguments are used in the format method, their values are referred to
+by using the name of the argument. ::
+
+ >>> print 'This {food} is {adjective}.'.format(food='spam', adjective='absolutely horrible')
+ This spam is absolutely horrible.
+
+Positional and keyword arguments can be arbitrarily combined::
+
+ >>> print 'The story of {0}, {1}, and {other}.'.format('Bill', 'Manfred', other='Georg')
+ The story of Bill, Manfred, and Georg.
+
+An optional ``':``` and format specifier can follow the field name. This also
+greater control over how the value is formatted. The following example
+truncates the Pi to three places after the decimal.
>>> import math
- >>> print('The value of PI is approximately %5.3f.' % math.pi)
+ >>> print('The value of PI is approximately {0:.3f}.'.format(math.pi))
The value of PI is approximately 3.142.
-If there is more than one format in the string, you need to pass a tuple as
-right operand, as in this example::
+Passing an integer after the ``':'`` will cause that field to be a minimum
+number of characters wide. This is useful for making tables pretty.::
>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 7678}
>>> for name, phone in table.items():
- ... print('%-10s ==> %10d' % (name, phone))
+ ... print('{0:10} ==> {1:10d}'.format(name, phone))
...
Jack ==> 4098
Dcab ==> 7678
Sjoerd ==> 4127
-Most formats work exactly as in C and require that you pass the proper type;
-however, if you don't you get an exception, not a core dump. The ``%s`` format
-is more relaxed: if the corresponding argument is not a string object, it is
-converted to string using the :func:`str` built-in function. Using ``*`` to
-pass the width or precision in as a separate (integer) argument is supported.
-The C formats ``%n`` and ``%p`` are not supported.
-
If you have a really long format string that you don't want to split up, it
would be nice if you could reference the variables to be formatted by name
-instead of by position. This can be done by using form ``%(name)format``, as
-shown here::
+instead of by position. This can be done by simply passing the dict and using
+square brackets ``'[]'`` to access the keys ::
>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678}
- >>> print('Jack: %(Jack)d; Sjoerd: %(Sjoerd)d; Dcab: %(Dcab)d' % table)
+ >>> print('Jack: {0[Jack]:d}; Sjoerd: {0[Sjoerd]:d}; Dcab: {0[Dcab]:d}'.format(table))
+ Jack: 4098; Sjoerd: 4127; Dcab: 8637678
+
+This could also be done by passing the table as keyword arguments with the '**'
+notation.::
+
+ >>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678}
+ >>> print('Jack: {Jack:d}; Sjoerd: {Sjoerd:d}; Dcab: {Dcab:d}'.format(**table))
Jack: 4098; Sjoerd: 4127; Dcab: 8637678
This is particularly useful in combination with the new built-in :func:`vars`
function, which returns a dictionary containing all local variables.
-The :mod:`string` module contains a class Template which offers yet another way
-to substitute values into strings.
+For a complete overview of string formating with :meth:`str.format`, see
+:ref:`formatstrings`.
+
+
+Old string formatting
+---------------------
+
+The ``%`` operator can also be used for string formatting. It interprets the
+left argument much like a :cfunc:`sprintf`\ -style format string to be applied
+to the right argument, and returns the string resulting from this formatting
+operation. For example::
+
+ >>> import math
+ >>> print 'The value of PI is approximately %5.3f.' % math.pi
+ The value of PI is approximately 3.142.
+
+Since :meth:`str.format` is quite new, a lot of Python code still uses the ``%``
+operator. However, because this old style of formatting will eventually removed
+from the language :meth:`str.format` should generally be used.
+
+More information can be found in the :ref:`old-string-formatting` section.
+
.. _tut-files:
Modified: python/branches/py3k/Doc/tutorial/introduction.rst
==============================================================================
--- python/branches/py3k/Doc/tutorial/introduction.rst (original)
+++ python/branches/py3k/Doc/tutorial/introduction.rst Mon May 26 03:03:56 2008
@@ -393,8 +393,12 @@
basic transformations and searching.
:ref:`string-formatting`
- The formatting operations invoked by the :meth:`format` string method are
- described in more detail here.
+ Information about string formatting with :meth:`str.format` is described
+ here.
+
+ :ref:`old-string-formatting`
+ The old formatting operations invoked when strings and Unicode strings are
+ the left operand of the ``%`` operator are described in more detail here.
.. _tut-unicodestrings:
Modified: python/branches/py3k/Doc/tutorial/stdlib2.rst
==============================================================================
--- python/branches/py3k/Doc/tutorial/stdlib2.rst (original)
+++ python/branches/py3k/Doc/tutorial/stdlib2.rst Mon May 26 03:03:56 2008
@@ -116,7 +116,7 @@
>>> for i, filename in enumerate(photofiles):
... base, ext = os.path.splitext(filename)
... newname = t.substitute(d=date, n=i, f=ext)
- ... print('%s --> %s' % (filename, newname))
+ ... print('{0} --> {1}'.format(filename, newname))
img_1074.jpg --> Ashley_0.jpg
img_1076.jpg --> Ashley_1.jpg
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