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Victor Zverovich 2012-12-18 06:49:18 -08:00
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add_custom_command(OUTPUT html/index.html
COMMAND sphinx-build -b html . ../html
DEPENDS conf.py index.rst)
add_custom_target(doc DEPENDS html/index.html)

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A. HISTORY OF THE SOFTWARE
==========================
Python was created in the early 1990s by Guido van Rossum at Stichting
Mathematisch Centrum (CWI, see http://www.cwi.nl) in the Netherlands
as a successor of a language called ABC. Guido remains Python's
principal author, although it includes many contributions from others.
In 1995, Guido continued his work on Python at the Corporation for
National Research Initiatives (CNRI, see http://www.cnri.reston.va.us)
in Reston, Virginia where he released several versions of the
software.
In May 2000, Guido and the Python core development team moved to
BeOpen.com to form the BeOpen PythonLabs team. In October of the same
year, the PythonLabs team moved to Digital Creations (now Zope
Corporation, see http://www.zope.com). In 2001, the Python Software
Foundation (PSF, see http://www.python.org/psf/) was formed, a
non-profit organization created specifically to own Python-related
Intellectual Property. Zope Corporation is a sponsoring member of
the PSF.
All Python releases are Open Source (see http://www.opensource.org for
the Open Source Definition). Historically, most, but not all, Python
releases have also been GPL-compatible; the table below summarizes
the various releases.
Release Derived Year Owner GPL-
from compatible? (1)
0.9.0 thru 1.2 1991-1995 CWI yes
1.3 thru 1.5.2 1.2 1995-1999 CNRI yes
1.6 1.5.2 2000 CNRI no
2.0 1.6 2000 BeOpen.com no
1.6.1 1.6 2001 CNRI yes (2)
2.1 2.0+1.6.1 2001 PSF no
2.0.1 2.0+1.6.1 2001 PSF yes
2.1.1 2.1+2.0.1 2001 PSF yes
2.2 2.1.1 2001 PSF yes
2.1.2 2.1.1 2002 PSF yes
2.1.3 2.1.2 2002 PSF yes
2.2.1 2.2 2002 PSF yes
2.2.2 2.2.1 2002 PSF yes
2.2.3 2.2.2 2003 PSF yes
2.3 2.2.2 2002-2003 PSF yes
2.3.1 2.3 2002-2003 PSF yes
2.3.2 2.3.1 2002-2003 PSF yes
2.3.3 2.3.2 2002-2003 PSF yes
2.3.4 2.3.3 2004 PSF yes
2.3.5 2.3.4 2005 PSF yes
2.4 2.3 2004 PSF yes
2.4.1 2.4 2005 PSF yes
2.4.2 2.4.1 2005 PSF yes
2.4.3 2.4.2 2006 PSF yes
2.4.4 2.4.3 2006 PSF yes
2.5 2.4 2006 PSF yes
2.5.1 2.5 2007 PSF yes
2.5.2 2.5.1 2008 PSF yes
2.5.3 2.5.2 2008 PSF yes
2.6 2.5 2008 PSF yes
2.6.1 2.6 2008 PSF yes
2.6.2 2.6.1 2009 PSF yes
2.6.3 2.6.2 2009 PSF yes
2.6.4 2.6.3 2009 PSF yes
2.6.5 2.6.4 2010 PSF yes
3.0 2.6 2008 PSF yes
3.0.1 3.0 2009 PSF yes
3.1 3.0.1 2009 PSF yes
3.1.1 3.1 2009 PSF yes
3.1.2 3.1.1 2010 PSF yes
3.1.3 3.1.2 2010 PSF yes
3.1.4 3.1.3 2011 PSF yes
3.2 3.1 2011 PSF yes
3.2.1 3.2 2011 PSF yes
3.2.2 3.2.1 2011 PSF yes
3.2.3 3.2.2 2012 PSF yes
3.3.0 3.2 2012 PSF yes
Footnotes:
(1) GPL-compatible doesn't mean that we're distributing Python under
the GPL. All Python licenses, unlike the GPL, let you distribute
a modified version without making your changes open source. The
GPL-compatible licenses make it possible to combine Python with
other software that is released under the GPL; the others don't.
(2) According to Richard Stallman, 1.6.1 is not GPL-compatible,
because its license has a choice of law clause. According to
CNRI, however, Stallman's lawyer has told CNRI's lawyer that 1.6.1
is "not incompatible" with the GPL.
Thanks to the many outside volunteers who have worked under Guido's
direction to make these releases possible.
B. TERMS AND CONDITIONS FOR ACCESSING OR OTHERWISE USING PYTHON
===============================================================
PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
--------------------------------------------
1. This LICENSE AGREEMENT is between the Python Software Foundation
("PSF"), and the Individual or Organization ("Licensee") accessing and
otherwise using this software ("Python") in source or binary form and
its associated documentation.
2. Subject to the terms and conditions of this License Agreement, PSF hereby
grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
analyze, test, perform and/or display publicly, prepare derivative works,
distribute, and otherwise use Python alone or in any derivative version,
provided, however, that PSF's License Agreement and PSF's notice of copyright,
i.e., "Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
2011, 2012 Python Software Foundation; All Rights Reserved" are retained in Python
alone or in any derivative version prepared by Licensee.
3. In the event Licensee prepares a derivative work that is based on
or incorporates Python or any part thereof, and wants to make
the derivative work available to others as provided herein, then
Licensee hereby agrees to include in any such work a brief summary of
the changes made to Python.
4. PSF is making Python available to Licensee on an "AS IS"
basis. PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
IMPLIED. BY WAY OF EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND
DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON WILL NOT
INFRINGE ANY THIRD PARTY RIGHTS.
5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS
A RESULT OF MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON,
OR ANY DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
6. This License Agreement will automatically terminate upon a material
breach of its terms and conditions.
7. Nothing in this License Agreement shall be deemed to create any
relationship of agency, partnership, or joint venture between PSF and
Licensee. This License Agreement does not grant permission to use PSF
trademarks or trade name in a trademark sense to endorse or promote
products or services of Licensee, or any third party.
8. By copying, installing or otherwise using Python, Licensee
agrees to be bound by the terms and conditions of this License
Agreement.
BEOPEN.COM LICENSE AGREEMENT FOR PYTHON 2.0
-------------------------------------------
BEOPEN PYTHON OPEN SOURCE LICENSE AGREEMENT VERSION 1
1. This LICENSE AGREEMENT is between BeOpen.com ("BeOpen"), having an
office at 160 Saratoga Avenue, Santa Clara, CA 95051, and the
Individual or Organization ("Licensee") accessing and otherwise using
this software in source or binary form and its associated
documentation ("the Software").
2. Subject to the terms and conditions of this BeOpen Python License
Agreement, BeOpen hereby grants Licensee a non-exclusive,
royalty-free, world-wide license to reproduce, analyze, test, perform
and/or display publicly, prepare derivative works, distribute, and
otherwise use the Software alone or in any derivative version,
provided, however, that the BeOpen Python License is retained in the
Software, alone or in any derivative version prepared by Licensee.
3. BeOpen is making the Software available to Licensee on an "AS IS"
basis. BEOPEN MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
IMPLIED. BY WAY OF EXAMPLE, BUT NOT LIMITATION, BEOPEN MAKES NO AND
DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF THE SOFTWARE WILL NOT
INFRINGE ANY THIRD PARTY RIGHTS.
4. BEOPEN SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF THE
SOFTWARE FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS
AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THE SOFTWARE, OR ANY
DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
5. This License Agreement will automatically terminate upon a material
breach of its terms and conditions.
6. This License Agreement shall be governed by and interpreted in all
respects by the law of the State of California, excluding conflict of
law provisions. Nothing in this License Agreement shall be deemed to
create any relationship of agency, partnership, or joint venture
between BeOpen and Licensee. This License Agreement does not grant
permission to use BeOpen trademarks or trade names in a trademark
sense to endorse or promote products or services of Licensee, or any
third party. As an exception, the "BeOpen Python" logos available at
http://www.pythonlabs.com/logos.html may be used according to the
permissions granted on that web page.
7. By copying, installing or otherwise using the software, Licensee
agrees to be bound by the terms and conditions of this License
Agreement.
CNRI LICENSE AGREEMENT FOR PYTHON 1.6.1
---------------------------------------
1. This LICENSE AGREEMENT is between the Corporation for National
Research Initiatives, having an office at 1895 Preston White Drive,
Reston, VA 20191 ("CNRI"), and the Individual or Organization
("Licensee") accessing and otherwise using Python 1.6.1 software in
source or binary form and its associated documentation.
2. Subject to the terms and conditions of this License Agreement, CNRI
hereby grants Licensee a nonexclusive, royalty-free, world-wide
license to reproduce, analyze, test, perform and/or display publicly,
prepare derivative works, distribute, and otherwise use Python 1.6.1
alone or in any derivative version, provided, however, that CNRI's
License Agreement and CNRI's notice of copyright, i.e., "Copyright (c)
1995-2001 Corporation for National Research Initiatives; All Rights
Reserved" are retained in Python 1.6.1 alone or in any derivative
version prepared by Licensee. Alternately, in lieu of CNRI's License
Agreement, Licensee may substitute the following text (omitting the
quotes): "Python 1.6.1 is made available subject to the terms and
conditions in CNRI's License Agreement. This Agreement together with
Python 1.6.1 may be located on the Internet using the following
unique, persistent identifier (known as a handle): 1895.22/1013. This
Agreement may also be obtained from a proxy server on the Internet
using the following URL: http://hdl.handle.net/1895.22/1013".
3. In the event Licensee prepares a derivative work that is based on
or incorporates Python 1.6.1 or any part thereof, and wants to make
the derivative work available to others as provided herein, then
Licensee hereby agrees to include in any such work a brief summary of
the changes made to Python 1.6.1.
4. CNRI is making Python 1.6.1 available to Licensee on an "AS IS"
basis. CNRI MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
IMPLIED. BY WAY OF EXAMPLE, BUT NOT LIMITATION, CNRI MAKES NO AND
DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON 1.6.1 WILL NOT
INFRINGE ANY THIRD PARTY RIGHTS.
5. CNRI SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
1.6.1 FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS
A RESULT OF MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 1.6.1,
OR ANY DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
6. This License Agreement will automatically terminate upon a material
breach of its terms and conditions.
7. This License Agreement shall be governed by the federal
intellectual property law of the United States, including without
limitation the federal copyright law, and, to the extent such
U.S. federal law does not apply, by the law of the Commonwealth of
Virginia, excluding Virginia's conflict of law provisions.
Notwithstanding the foregoing, with regard to derivative works based
on Python 1.6.1 that incorporate non-separable material that was
previously distributed under the GNU General Public License (GPL), the
law of the Commonwealth of Virginia shall govern this License
Agreement only as to issues arising under or with respect to
Paragraphs 4, 5, and 7 of this License Agreement. Nothing in this
License Agreement shall be deemed to create any relationship of
agency, partnership, or joint venture between CNRI and Licensee. This
License Agreement does not grant permission to use CNRI trademarks or
trade name in a trademark sense to endorse or promote products or
services of Licensee, or any third party.
8. By clicking on the "ACCEPT" button where indicated, or by copying,
installing or otherwise using Python 1.6.1, Licensee agrees to be
bound by the terms and conditions of this License Agreement.
ACCEPT
CWI LICENSE AGREEMENT FOR PYTHON 0.9.0 THROUGH 1.2
--------------------------------------------------
Copyright (c) 1991 - 1995, Stichting Mathematisch Centrum Amsterdam,
The Netherlands. All rights reserved.
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of Stichting Mathematisch
Centrum or CWI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.
STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

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# -*- coding: utf-8 -*-
#
# format documentation build configuration file, created by
# sphinx-quickstart on Tue Dec 18 06:46:16 2012.
#
# This file is execfile()d with the current directory set to its containing dir.
#
# Note that not all possible configuration values are present in this
# autogenerated file.
#
# All configuration values have a default; values that are commented out
# serve to show the default.
import sys, os
# If extensions (or modules to document with autodoc) are in another directory,
# add these directories to sys.path here. If the directory is relative to the
# documentation root, use os.path.abspath to make it absolute, like shown here.
#sys.path.insert(0, os.path.abspath('.'))
# -- General configuration -----------------------------------------------------
# If your documentation needs a minimal Sphinx version, state it here.
#needs_sphinx = '1.0'
# Add any Sphinx extension module names here, as strings. They can be extensions
# coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
extensions = ['sphinx.ext.mathjax']
# Add any paths that contain templates here, relative to this directory.
templates_path = ['-templates']
# The suffix of source filenames.
source_suffix = '.rst'
# The encoding of source files.
#source_encoding = 'utf-8-sig'
# The master toctree document.
master_doc = 'index'
# General information about the project.
project = u'format'
copyright = u'2012, Victor Zverovich'
# The version info for the project you're documenting, acts as replacement for
# |version| and |release|, also used in various other places throughout the
# built documents.
#
# The short X.Y version.
version = '0.1'
# The full version, including alpha/beta/rc tags.
release = '0.1'
# The language for content autogenerated by Sphinx. Refer to documentation
# for a list of supported languages.
#language = None
# There are two options for replacing |today|: either, you set today to some
# non-false value, then it is used:
#today = ''
# Else, today_fmt is used as the format for a strftime call.
#today_fmt = '%B %d, %Y'
# List of patterns, relative to source directory, that match files and
# directories to ignore when looking for source files.
exclude_patterns = []
# The reST default role (used for this markup: `text`) to use for all documents.
#default_role = None
# If true, '()' will be appended to :func: etc. cross-reference text.
#add_function_parentheses = True
# If true, the current module name will be prepended to all description
# unit titles (such as .. function::).
#add_module_names = True
# If true, sectionauthor and moduleauthor directives will be shown in the
# output. They are ignored by default.
#show_authors = False
# The name of the Pygments (syntax highlighting) style to use.
pygments_style = 'sphinx'
# A list of ignored prefixes for module index sorting.
#modindex_common_prefix = []
# -- Options for HTML output ---------------------------------------------------
# The theme to use for HTML and HTML Help pages. See the documentation for
# a list of builtin themes.
html_theme = 'default'
# Theme options are theme-specific and customize the look and feel of a theme
# further. For a list of options available for each theme, see the
# documentation.
#html_theme_options = {}
# Add any paths that contain custom themes here, relative to this directory.
#html_theme_path = []
# The name for this set of Sphinx documents. If None, it defaults to
# "<project> v<release> documentation".
#html_title = None
# A shorter title for the navigation bar. Default is the same as html_title.
#html_short_title = None
# The name of an image file (relative to this directory) to place at the top
# of the sidebar.
#html_logo = None
# The name of an image file (within the static path) to use as favicon of the
# docs. This file should be a Windows icon file (.ico) being 16x16 or 32x32
# pixels large.
#html_favicon = None
# Add any paths that contain custom static files (such as style sheets) here,
# relative to this directory. They are copied after the builtin static files,
# so a file named "default.css" will overwrite the builtin "default.css".
html_static_path = ['-static']
# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
# using the given strftime format.
#html_last_updated_fmt = '%b %d, %Y'
# If true, SmartyPants will be used to convert quotes and dashes to
# typographically correct entities.
#html_use_smartypants = True
# Custom sidebar templates, maps document names to template names.
#html_sidebars = {}
# Additional templates that should be rendered to pages, maps page names to
# template names.
#html_additional_pages = {}
# If false, no module index is generated.
#html_domain_indices = True
# If false, no index is generated.
#html_use_index = True
# If true, the index is split into individual pages for each letter.
#html_split_index = False
# If true, links to the reST sources are added to the pages.
#html_show_sourcelink = True
# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
#html_show_sphinx = True
# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
#html_show_copyright = True
# If true, an OpenSearch description file will be output, and all pages will
# contain a <link> tag referring to it. The value of this option must be the
# base URL from which the finished HTML is served.
#html_use_opensearch = ''
# This is the file name suffix for HTML files (e.g. ".xhtml").
#html_file_suffix = None
# Output file base name for HTML help builder.
htmlhelp_basename = 'formatdoc'
# -- Options for LaTeX output --------------------------------------------------
latex_elements = {
# The paper size ('letterpaper' or 'a4paper').
#'papersize': 'letterpaper',
# The font size ('10pt', '11pt' or '12pt').
#'pointsize': '10pt',
# Additional stuff for the LaTeX preamble.
#'preamble': '',
}
# Grouping the document tree into LaTeX files. List of tuples
# (source start file, target name, title, author, documentclass [howto/manual]).
latex_documents = [
('index', 'format.tex', u'format Documentation',
u'Victor Zverovich', 'manual'),
]
# The name of an image file (relative to this directory) to place at the top of
# the title page.
#latex_logo = None
# For "manual" documents, if this is true, then toplevel headings are parts,
# not chapters.
#latex_use_parts = False
# If true, show page references after internal links.
#latex_show_pagerefs = False
# If true, show URL addresses after external links.
#latex_show_urls = False
# Documents to append as an appendix to all manuals.
#latex_appendices = []
# If false, no module index is generated.
#latex_domain_indices = True
# -- Options for manual page output --------------------------------------------
# One entry per manual page. List of tuples
# (source start file, name, description, authors, manual section).
man_pages = [
('index', 'format', u'format Documentation',
[u'Victor Zverovich'], 1)
]
# If true, show URL addresses after external links.
#man_show_urls = False
# -- Options for Texinfo output ------------------------------------------------
# Grouping the document tree into Texinfo files. List of tuples
# (source start file, target name, title, author,
# dir menu entry, description, category)
texinfo_documents = [
('index', 'format', u'format Documentation',
u'Victor Zverovich', 'format', 'One line description of project.',
'Miscellaneous'),
]
# Documents to append as an appendix to all manuals.
#texinfo_appendices = []
# If false, no module index is generated.
#texinfo_domain_indices = True
# How to display URL addresses: 'footnote', 'no', or 'inline'.
#texinfo_show_urls = 'footnote'

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.. format documentation master file, created by
sphinx-quickstart on Tue Dec 18 06:46:16 2012.
You can adapt this file completely to your liking, but it should at least
contain the root `toctree` directive.
Welcome to format's documentation!
==================================
Contents:
.. toctree::
:maxdepth: 2
Indices and tables
==================
* :ref:`genindex`
* :ref:`modindex`
* :ref:`search`

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.. _string-formatting:
String Formatting
-----------------
The built-in string class provides the ability to do complex variable
substitutions and value formatting via the :func:`format` method described in
:pep:`3101`. The :class:`Formatter` class in the :mod:`string` module allows
you to create and customize your own string formatting behaviors using the same
implementation as the built-in :meth:`format` method.
.. class:: Formatter
The :class:`Formatter` class has the following public methods:
.. method:: format(format_string, *args, **kwargs)
:meth:`format` is the primary API method. It takes a format string and
an arbitrary set of positional and keyword arguments.
:meth:`format` is just a wrapper that calls :meth:`vformat`.
.. method:: vformat(format_string, args, kwargs)
This function does the actual work of formatting. It is exposed as a
separate function for cases where you want to pass in a predefined
dictionary of arguments, rather than unpacking and repacking the
dictionary as individual arguments using the ``*args`` and ``**kwds``
syntax. :meth:`vformat` does the work of breaking up the format string
into character data and replacement fields. It calls the various
methods described below.
In addition, the :class:`Formatter` defines a number of methods that are
intended to be replaced by subclasses:
.. method:: parse(format_string)
Loop over the format_string and return an iterable of tuples
(*literal_text*, *field_name*, *format_spec*, *conversion*). This is used
by :meth:`vformat` to break the string into either literal text, or
replacement fields.
The values in the tuple conceptually represent a span of literal text
followed by a single replacement field. If there is no literal text
(which can happen if two replacement fields occur consecutively), then
*literal_text* will be a zero-length string. If there is no replacement
field, then the values of *field_name*, *format_spec* and *conversion*
will be ``None``.
.. method:: get_field(field_name, args, kwargs)
Given *field_name* as returned by :meth:`parse` (see above), convert it to
an object to be formatted. Returns a tuple (obj, used_key). The default
version takes strings of the form defined in :pep:`3101`, such as
"0[name]" or "label.title". *args* and *kwargs* are as passed in to
:meth:`vformat`. The return value *used_key* has the same meaning as the
*key* parameter to :meth:`get_value`.
.. method:: get_value(key, args, kwargs)
Retrieve a given field value. The *key* argument will be either an
integer or a string. If it is an integer, it represents the index of the
positional argument in *args*; if it is a string, then it represents a
named argument in *kwargs*.
The *args* parameter is set to the list of positional arguments to
:meth:`vformat`, and the *kwargs* parameter is set to the dictionary of
keyword arguments.
For compound field names, these functions are only called for the first
component of the field name; Subsequent components are handled through
normal attribute and indexing operations.
So for example, the field expression '0.name' would cause
:meth:`get_value` to be called with a *key* argument of 0. The ``name``
attribute will be looked up after :meth:`get_value` returns by calling the
built-in :func:`getattr` function.
If the index or keyword refers to an item that does not exist, then an
:exc:`IndexError` or :exc:`KeyError` should be raised.
.. method:: check_unused_args(used_args, args, kwargs)
Implement checking for unused arguments if desired. The arguments to this
function is the set of all argument keys that were actually referred to in
the format string (integers for positional arguments, and strings for
named arguments), and a reference to the *args* and *kwargs* that was
passed to vformat. The set of unused args can be calculated from these
parameters. :meth:`check_unused_args` is assumed to raise an exception if
the check fails.
.. method:: format_field(value, format_spec)
:meth:`format_field` simply calls the global :func:`format` built-in. The
method is provided so that subclasses can override it.
.. method:: convert_field(value, conversion)
Converts the value (returned by :meth:`get_field`) given a conversion type
(as in the tuple returned by the :meth:`parse` method). The default
version understands 's' (str), 'r' (repr) and 'a' (ascii) conversion
types.
.. _formatstrings:
Format String Syntax
--------------------
The :meth:`str.format` method and the :class:`Formatter` class share the same
syntax for format strings (although in the case of :class:`Formatter`,
subclasses can define their own format string syntax).
Format strings contain "replacement fields" surrounded by curly braces ``{}``.
Anything that is not contained in braces is considered literal text, which is
copied unchanged to the output. If you need to include a brace character in the
literal text, it can be escaped by doubling: ``{{`` and ``}}``.
The grammar for a replacement field is as follows:
.. productionlist:: sf
replacement_field: "{" [`field_name`] ["!" `conversion`] [":" `format_spec`] "}"
field_name: arg_name ("." `attribute_name` | "[" `element_index` "]")*
arg_name: [`identifier` | `integer`]
attribute_name: `identifier`
element_index: `integer` | `index_string`
index_string: <any source character except "]"> +
conversion: "r" | "s" | "a"
format_spec: <described in the next section>
In less formal terms, the replacement field can start with a *field_name* that specifies
the object whose value is to be formatted and inserted
into the output instead of the replacement field.
The *field_name* is optionally followed by a *conversion* field, which is
preceded by an exclamation point ``'!'``, and a *format_spec*, which is preceded
by a colon ``':'``. These specify a non-default format for the replacement value.
See also the :ref:`formatspec` section.
The *field_name* itself begins with an *arg_name* that is either a number or a
keyword. If it's a number, it refers to a positional argument, and if it's a keyword,
it refers to a named keyword argument. If the numerical arg_names in a format string
are 0, 1, 2, ... in sequence, they can all be omitted (not just some)
and the numbers 0, 1, 2, ... will be automatically inserted in that order.
Because *arg_name* is not quote-delimited, it is not possible to specify arbitrary
dictionary keys (e.g., the strings ``'10'`` or ``':-]'``) within a format string.
The *arg_name* can be followed by any number of index or
attribute expressions. An expression of the form ``'.name'`` selects the named
attribute using :func:`getattr`, while an expression of the form ``'[index]'``
does an index lookup using :func:`__getitem__`.
.. versionchanged:: 3.1
The positional argument specifiers can be omitted, so ``'{} {}'`` is
equivalent to ``'{0} {1}'``.
Some simple format string examples::
"First, thou shalt count to {0}" # References first positional argument
"Bring me a {}" # Implicitly references the first positional argument
"From {} to {}" # Same as "From {0} to {1}"
"My quest is {name}" # References keyword argument 'name'
"Weight in tons {0.weight}" # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}" # First element of keyword argument 'players'.
The *conversion* field causes a type coercion before formatting. Normally, the
job of formatting a value is done by the :meth:`__format__` method of the value
itself. However, in some cases it is desirable to force a type to be formatted
as a string, overriding its own definition of formatting. By converting the
value to a string before calling :meth:`__format__`, the normal formatting logic
is bypassed.
Three conversion flags are currently supported: ``'!s'`` which calls :func:`str`
on the value, ``'!r'`` which calls :func:`repr` and ``'!a'`` which calls
:func:`ascii`.
Some examples::
"Harold's a clever {0!s}" # Calls str() on the argument first
"Bring out the holy {name!r}" # Calls repr() on the argument first
"More {!a}" # Calls ascii() on the argument first
The *format_spec* field contains a specification of how the value should be
presented, including such details as field width, alignment, padding, decimal
precision and so on. Each value type can define its own "formatting
mini-language" or interpretation of the *format_spec*.
Most built-in types support a common formatting mini-language, which is
described in the next section.
A *format_spec* field can also include nested replacement fields within it.
These nested replacement fields can contain only a field name; conversion flags
and format specifications are not allowed. The replacement fields within the
format_spec are substituted before the *format_spec* string is interpreted.
This allows the formatting of a value to be dynamically specified.
See the :ref:`formatexamples` section for some examples.
.. _formatspec:
Format Specification Mini-Language
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"Format specifications" are used within replacement fields contained within a
format string to define how individual values are presented (see
:ref:`formatstrings`). They can also be passed directly to the built-in
:func:`format` function. Each formattable type may define how the format
specification is to be interpreted.
Most built-in types implement the following options for format specifications,
although some of the formatting options are only supported by the numeric types.
A general convention is that an empty format string (``""``) produces
the same result as if you had called :func:`str` on the value. A
non-empty format string typically modifies the result.
The general form of a *standard format specifier* is:
.. productionlist:: sf
format_spec: [[`fill`]`align`][`sign`][#][0][`width`][,][.`precision`][`type`]
fill: <a character other than '{' or '}'>
align: "<" | ">" | "=" | "^"
sign: "+" | "-" | " "
width: `integer`
precision: `integer`
type: "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
The *fill* character can be any character other than '{' or '}'. The presence
of a fill character is signaled by the character following it, which must be
one of the alignment options. If the second character of *format_spec* is not
a valid alignment option, then it is assumed that both the fill character and
the alignment option are absent.
The meaning of the various alignment options is as follows:
+---------+----------------------------------------------------------+
| Option | Meaning |
+=========+==========================================================+
| ``'<'`` | Forces the field to be left-aligned within the available |
| | space (this is the default for most objects). |
+---------+----------------------------------------------------------+
| ``'>'`` | Forces the field to be right-aligned within the |
| | available space (this is the default for numbers). |
+---------+----------------------------------------------------------+
| ``'='`` | Forces the padding to be placed after the sign (if any) |
| | but before the digits. This is used for printing fields |
| | in the form '+000000120'. This alignment option is only |
| | valid for numeric types. |
+---------+----------------------------------------------------------+
| ``'^'`` | Forces the field to be centered within the available |
| | space. |
+---------+----------------------------------------------------------+
Note that unless a minimum field width is defined, the field width will always
be the same size as the data to fill it, so that the alignment option has no
meaning in this case.
The *sign* option is only valid for number types, and can be one of the
following:
+---------+----------------------------------------------------------+
| Option | Meaning |
+=========+==========================================================+
| ``'+'`` | indicates that a sign should be used for both |
| | positive as well as negative numbers. |
+---------+----------------------------------------------------------+
| ``'-'`` | indicates that a sign should be used only for negative |
| | numbers (this is the default behavior). |
+---------+----------------------------------------------------------+
| space | indicates that a leading space should be used on |
| | positive numbers, and a minus sign on negative numbers. |
+---------+----------------------------------------------------------+
The ``'#'`` option causes the "alternate form" to be used for the
conversion. The alternate form is defined differently for different
types. This option is only valid for integer, float, complex and
Decimal types. For integers, when binary, octal, or hexadecimal output
is used, this option adds the prefix respective ``'0b'``, ``'0o'``, or
``'0x'`` to the output value. For floats, complex and Decimal the
alternate form causes the result of the conversion to always contain a
decimal-point character, even if no digits follow it. Normally, a
decimal-point character appears in the result of these conversions
only if a digit follows it. In addition, for ``'g'`` and ``'G'``
conversions, trailing zeros are not removed from the result.
The ``','`` option signals the use of a comma for a thousands separator.
For a locale aware separator, use the ``'n'`` integer presentation type
instead.
.. versionchanged:: 3.1
Added the ``','`` option (see also :pep:`378`).
*width* is a decimal integer defining the minimum field width. If not
specified, then the field width will be determined by the content.
Preceding the *width* field by a zero (``'0'``) character enables
sign-aware zero-padding for numeric types. This is equivalent to a *fill*
character of ``'0'`` with an *alignment* type of ``'='``.
The *precision* is a decimal number indicating how many digits should be
displayed after the decimal point for a floating point value formatted with
``'f'`` and ``'F'``, or before and after the decimal point for a floating point
value formatted with ``'g'`` or ``'G'``. For non-number types the field
indicates the maximum field size - in other words, how many characters will be
used from the field content. The *precision* is not allowed for integer values.
Finally, the *type* determines how the data should be presented.
The available string presentation types are:
+---------+----------------------------------------------------------+
| Type | Meaning |
+=========+==========================================================+
| ``'s'`` | String format. This is the default type for strings and |
| | may be omitted. |
+---------+----------------------------------------------------------+
| None | The same as ``'s'``. |
+---------+----------------------------------------------------------+
The available integer presentation types are:
+---------+----------------------------------------------------------+
| Type | Meaning |
+=========+==========================================================+
| ``'b'`` | Binary format. Outputs the number in base 2. |
+---------+----------------------------------------------------------+
| ``'c'`` | Character. Converts the integer to the corresponding |
| | unicode character before printing. |
+---------+----------------------------------------------------------+
| ``'d'`` | Decimal Integer. Outputs the number in base 10. |
+---------+----------------------------------------------------------+
| ``'o'`` | Octal format. Outputs the number in base 8. |
+---------+----------------------------------------------------------+
| ``'x'`` | Hex format. Outputs the number in base 16, using lower- |
| | case letters for the digits above 9. |
+---------+----------------------------------------------------------+
| ``'X'`` | Hex format. Outputs the number in base 16, using upper- |
| | case letters for the digits above 9. |
+---------+----------------------------------------------------------+
| ``'n'`` | Number. This is the same as ``'d'``, except that it uses |
| | the current locale setting to insert the appropriate |
| | number separator characters. |
+---------+----------------------------------------------------------+
| None | The same as ``'d'``. |
+---------+----------------------------------------------------------+
In addition to the above presentation types, integers can be formatted
with the floating point presentation types listed below (except
``'n'`` and None). When doing so, :func:`float` is used to convert the
integer to a floating point number before formatting.
The available presentation types for floating point and decimal values are:
+---------+----------------------------------------------------------+
| Type | Meaning |
+=========+==========================================================+
| ``'e'`` | Exponent notation. Prints the number in scientific |
| | notation using the letter 'e' to indicate the exponent. |
+---------+----------------------------------------------------------+
| ``'E'`` | Exponent notation. Same as ``'e'`` except it uses an |
| | upper case 'E' as the separator character. |
+---------+----------------------------------------------------------+
| ``'f'`` | Fixed point. Displays the number as a fixed-point |
| | number. |
+---------+----------------------------------------------------------+
| ``'F'`` | Fixed point. Same as ``'f'``, but converts ``nan`` to |
| | ``NAN`` and ``inf`` to ``INF``. |
+---------+----------------------------------------------------------+
| ``'g'`` | General format. For a given precision ``p >= 1``, |
| | this rounds the number to ``p`` significant digits and |
| | then formats the result in either fixed-point format |
| | or in scientific notation, depending on its magnitude. |
| | |
| | The precise rules are as follows: suppose that the |
| | result formatted with presentation type ``'e'`` and |
| | precision ``p-1`` would have exponent ``exp``. Then |
| | if ``-4 <= exp < p``, the number is formatted |
| | with presentation type ``'f'`` and precision |
| | ``p-1-exp``. Otherwise, the number is formatted |
| | with presentation type ``'e'`` and precision ``p-1``. |
| | In both cases insignificant trailing zeros are removed |
| | from the significand, and the decimal point is also |
| | removed if there are no remaining digits following it. |
| | |
| | Positive and negative infinity, positive and negative |
| | zero, and nans, are formatted as ``inf``, ``-inf``, |
| | ``0``, ``-0`` and ``nan`` respectively, regardless of |
| | the precision. |
| | |
| | A precision of ``0`` is treated as equivalent to a |
| | precision of ``1``. |
+---------+----------------------------------------------------------+
| ``'G'`` | General format. Same as ``'g'`` except switches to |
| | ``'E'`` if the number gets too large. The |
| | representations of infinity and NaN are uppercased, too. |
+---------+----------------------------------------------------------+
| ``'n'`` | Number. This is the same as ``'g'``, except that it uses |
| | the current locale setting to insert the appropriate |
| | number separator characters. |
+---------+----------------------------------------------------------+
| ``'%'`` | Percentage. Multiplies the number by 100 and displays |
| | in fixed (``'f'``) format, followed by a percent sign. |
+---------+----------------------------------------------------------+
| None | Similar to ``'g'``, except with at least one digit past |
| | the decimal point and a default precision of 12. This is |
| | intended to match :func:`str`, except you can add the |
| | other format modifiers. |
+---------+----------------------------------------------------------+
.. _formatexamples:
Format examples
^^^^^^^^^^^^^^^
This section contains examples of the new format syntax and comparison with
the old ``%``-formatting.
In most of the cases the syntax is similar to the old ``%``-formatting, with the
addition of the ``{}`` and with ``:`` used instead of ``%``.
For example, ``'%03.2f'`` can be translated to ``'{:03.2f}'``.
The new format syntax also supports new and different options, shown in the
follow examples.
Accessing arguments by position::
>>> '{0}, {1}, {2}'.format('a', 'b', 'c')
'a, b, c'
>>> '{}, {}, {}'.format('a', 'b', 'c') # 3.1+ only
'a, b, c'
>>> '{2}, {1}, {0}'.format('a', 'b', 'c')
'c, b, a'
>>> '{2}, {1}, {0}'.format(*'abc') # unpacking argument sequence
'c, b, a'
>>> '{0}{1}{0}'.format('abra', 'cad') # arguments' indices can be repeated
'abracadabra'
Accessing arguments by name::
>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W')
'Coordinates: 37.24N, -115.81W'
>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'}
>>> 'Coordinates: {latitude}, {longitude}'.format(**coord)
'Coordinates: 37.24N, -115.81W'
Accessing arguments' attributes::
>>> c = 3-5j
>>> ('The complex number {0} is formed from the real part {0.real} '
... 'and the imaginary part {0.imag}.').format(c)
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'
>>> class Point:
... def __init__(self, x, y):
... self.x, self.y = x, y
... def __str__(self):
... return 'Point({self.x}, {self.y})'.format(self=self)
...
>>> str(Point(4, 2))
'Point(4, 2)'
Accessing arguments' items::
>>> coord = (3, 5)
>>> 'X: {0[0]}; Y: {0[1]}'.format(coord)
'X: 3; Y: 5'
Replacing ``%s`` and ``%r``::
>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"
Aligning the text and specifying a width::
>>> '{:<30}'.format('left aligned')
'left aligned '
>>> '{:>30}'.format('right aligned')
' right aligned'
>>> '{:^30}'.format('centered')
' centered '
>>> '{:*^30}'.format('centered') # use '*' as a fill char
'***********centered***********'
Replacing ``%+f``, ``%-f``, and ``% f`` and specifying a sign::
>>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it always
'+3.140000; -3.140000'
>>> '{: f}; {: f}'.format(3.14, -3.14) # show a space for positive numbers
' 3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the minus -- same as '{:f}; {:f}'
'3.140000; -3.140000'
Replacing ``%x`` and ``%o`` and converting the value to different bases::
>>> # format also supports binary numbers
>>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}".format(42)
'int: 42; hex: 2a; oct: 52; bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42)
'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'
Using the comma as a thousands separator::
>>> '{:,}'.format(1234567890)
'1,234,567,890'
Expressing a percentage::
>>> points = 19
>>> total = 22
>>> 'Correct answers: {:.2%}'.format(points/total)
'Correct answers: 86.36%'
Using type-specific formatting::
>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'
Nesting arguments and more complex examples::
>>> for align, text in zip('<^>', ['left', 'center', 'right']):
... '{0:{fill}{align}16}'.format(text, fill=align, align=align)
...
'left<<<<<<<<<<<<'
'^^^^^center^^^^^'
'>>>>>>>>>>>right'
>>>
>>> octets = [192, 168, 0, 1]
>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)
'C0A80001'
>>> int(_, 16)
3232235521
>>>
>>> width = 5
>>> for num in range(5,12):
... for base in 'dXob':
... print('{0:{width}{base}}'.format(num, base=base, width=width), end=' ')
... print()
...
5 5 5 101
6 6 6 110
7 7 7 111
8 8 10 1000
9 9 11 1001
10 A 12 1010
11 B 13 1011