[OpenSPARC-T2-SAM] / sam-t2 / devtools / amd64 / html / python / lib / typesseq.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="lib.html" title='Python Library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="types-set.html" />
<link rel="prev" href="typeiter.html" />
<link rel="parent" href="types.html" />
<link rel="next" href="string-methods.html" />
<meta name='aesop' content='information' />
<title>2.3.6 Sequence Types -- str, unicode, list, tuple, buffer, xrange </title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="2.3.5 Iterator Types"
  href="typeiter.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="2.3 Built-in Types"
  href="types.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="2.3.6.1 String Methods"
  href="string-methods.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="typeiter.html">2.3.5 Iterator Types</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="types.html">2.3 Built-in Types</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="string-methods.html">2.3.6.1 String Methods</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->

<H2><A NAME="SECTION004360000000000000000"></A><A NAME="typesseq"></A>
<BR>
2.3.6 Sequence Types --
	    <tt class="class">str</tt>, <tt class="class">unicode</tt>, <tt class="class">list</tt>,
	    <tt class="class">tuple</tt>, <tt class="class">buffer</tt>, <tt class="class">xrange</tt>
	    
</H2>

<P>
There are six sequence types: strings, Unicode strings, lists,
tuples, buffers, and xrange objects.

<P>
String literals are written in single or double quotes:
<code>'xyzzy'</code>, <code>"frobozz"</code>.  See chapter 2 of the
<em class="citetitle"><a
 href="../ref/strings.html"
 title="Python Reference Manual"
 >Python Reference Manual</a></em> for more about
string literals.  Unicode strings are much like strings, but are
specified in the syntax using a preceding "<tt class="character">u</tt>" character:
<code>u'abc'</code>, <code>u"def"</code>.  Lists are constructed with square brackets,
separating items with commas: <code>[a, b, c]</code>.  Tuples are
constructed by the comma operator (not within square brackets), with
or without enclosing parentheses, but an empty tuple must have the
enclosing parentheses, such as <code>a, b, c</code> or <code>()</code>.  A single
item tuple must have a trailing comma, such as <code>(d,)</code>.
<a id='l2h-156' xml:id='l2h-156'></a><a id='l2h-157' xml:id='l2h-157'></a><a id='l2h-158' xml:id='l2h-158'></a><a id='l2h-159' xml:id='l2h-159'></a><a id='l2h-160' xml:id='l2h-160'></a>
<P>
Buffer objects are not directly supported by Python syntax, but can be
created by calling the builtin function
<tt class="function">buffer()</tt>.<a id='l2h-161' xml:id='l2h-161'></a>  They don't support
concatenation or repetition.
<a id='l2h-162' xml:id='l2h-162'></a>
<P>
Xrange objects are similar to buffers in that there is no specific
syntax to create them, but they are created using the <tt class="function">xrange()</tt>
function.<a id='l2h-163' xml:id='l2h-163'></a>  They don't support slicing,
concatenation or repetition, and using <code>in</code>, <code>not in</code>,
<tt class="function">min()</tt> or <tt class="function">max()</tt> on them is inefficient.
<a id='l2h-164' xml:id='l2h-164'></a>
<P>
Most sequence types support the following operations.  The "<tt class="samp">in</tt>" and
"<tt class="samp">not in</tt>" operations have the same priorities as the comparison
operations.  The "<tt class="samp">+</tt>" and "<tt class="samp">*</tt>" operations have the same
priority as the corresponding numeric operations.<A NAME="tex2html8"
  HREF="#foot1961"><SUP>2.7</SUP></A>
<P>
This table lists the sequence operations sorted in ascending priority
(operations in the same box have the same priority).  In the table,
<var>s</var> and <var>t</var> are sequences of the same type; <var>n</var>, <var>i</var>
and <var>j</var> are integers:

<P>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="center">Operation</th>
      <th class="left"  >Result</th>
      <th class="center">Notes</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="center" valign="baseline"><code><var>x</var> in <var>s</var></code></td>
        <td class="left"  ><code>True</code> if an item of <var>s</var> is equal to <var>x</var>, else <code>False</code></td>
        <td class="center">(1)</td></tr>
    <tr><td class="center" valign="baseline"><code><var>x</var> not in <var>s</var></code></td>
        <td class="left"  ><code>False</code> if an item of <var>s</var> is
equal to <var>x</var>, else <code>True</code></td>
        <td class="center">(1)</td></tr>
  
    <tr><td class="center" valign="baseline"><code><var>s</var> + <var>t</var></code></td>
        <td class="left"  >the concatenation of <var>s</var> and <var>t</var></td>
        <td class="center">(6)</td></tr>
    <tr><td class="center" valign="baseline"><code><var>s</var> * <var>n</var> , <var>n</var> * <var>s</var></code></td>
        <td class="left"  ><var>n</var> shallow copies of <var>s</var> concatenated</td>
        <td class="center">(2)</td></tr>
  
    <tr><td class="center" valign="baseline"><code><var>s</var>[<var>i</var>]</code></td>
        <td class="left"  ><var>i</var>'th item of <var>s</var>, origin 0</td>
        <td class="center">(3)</td></tr>
    <tr><td class="center" valign="baseline"><code><var>s</var>[<var>i</var>:<var>j</var>]</code></td>
        <td class="left"  >slice of <var>s</var> from <var>i</var> to <var>j</var></td>
        <td class="center">(3), (4)</td></tr>
    <tr><td class="center" valign="baseline"><code><var>s</var>[<var>i</var>:<var>j</var>:<var>k</var>]</code></td>
        <td class="left"  >slice of <var>s</var> from <var>i</var> to <var>j</var> with step <var>k</var></td>
        <td class="center">(3), (5)</td></tr>
  
    <tr><td class="center" valign="baseline"><code>len(<var>s</var>)</code></td>
        <td class="left"  >length of <var>s</var></td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>min(<var>s</var>)</code></td>
        <td class="left"  >smallest item of <var>s</var></td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>max(<var>s</var>)</code></td>
        <td class="left"  >largest item of <var>s</var></td>
        <td class="center"></td></tr></tbody>
</table></div>
<a id='l2h-165' xml:id='l2h-165'></a><a id='l2h-166' xml:id='l2h-166'></a><a id='l2h-167' xml:id='l2h-167'></a><a id='l2h-168' xml:id='l2h-168'></a><a id='l2h-169' xml:id='l2h-169'></a><a id='l2h-170' xml:id='l2h-170'></a><a id='l2h-171' xml:id='l2h-171'></a><a id='l2h-172' xml:id='l2h-172'></a><a id='l2h-173' xml:id='l2h-173'></a><a id='l2h-174' xml:id='l2h-174'></a><a id='l2h-175' xml:id='l2h-175'></a>
<P>
Notes:

<P>
<DL>
<DT><STRONG>(1)</STRONG></DT>
<DD>When <var>s</var> is a string or Unicode string object the
<code>in</code> and <code>not in</code> operations act like a substring test.  In
Python versions before 2.3, <var>x</var> had to be a string of length 1.
In Python 2.3 and beyond, <var>x</var> may be a string of any length.

<P>
</DD>
<DT><STRONG>(2)</STRONG></DT>
<DD>Values of <var>n</var> less than <code>0</code> are treated as
  <code>0</code> (which yields an empty sequence of the same type as
  <var>s</var>).  Note also that the copies are shallow; nested structures
  are not copied.  This often haunts new Python programmers; consider:

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; lists = [[]] * 3
&gt;&gt;&gt; lists
[[], [], []]
&gt;&gt;&gt; lists[0].append(3)
&gt;&gt;&gt; lists
[[3], [3], [3]]
</pre></div>

<P>
What has happened is that <code>[[]]</code> is a one-element list containing
  an empty list, so all three elements of <code>[[]] * 3</code> are (pointers to)
  this single empty list.  Modifying any of the elements of <code>lists</code>
  modifies this single list.  You can create a list of different lists this
  way:

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; lists = [[] for i in range(3)]
&gt;&gt;&gt; lists[0].append(3)
&gt;&gt;&gt; lists[1].append(5)
&gt;&gt;&gt; lists[2].append(7)
&gt;&gt;&gt; lists
[[3], [5], [7]]
</pre></div>

<P>
</DD>
<DT><STRONG>(3)</STRONG></DT>
<DD>If <var>i</var> or <var>j</var> is negative, the index is relative to
  the end of the string: <code>len(<var>s</var>) + <var>i</var></code> or
  <code>len(<var>s</var>) + <var>j</var></code> is substituted.  But note that <code>-0</code> is
  still <code>0</code>.

<P>
</DD>
<DT><STRONG>(4)</STRONG></DT>
<DD>The slice of <var>s</var> from <var>i</var> to <var>j</var> is defined as
  the sequence of items with index <var>k</var> such that <code><var>i</var> &lt;=
  <var>k</var> &lt; <var>j</var></code>.  If <var>i</var> or <var>j</var> is greater than
  <code>len(<var>s</var>)</code>, use <code>len(<var>s</var>)</code>.  If <var>i</var> is omitted,
  use <code>0</code>.  If <var>j</var> is omitted, use <code>len(<var>s</var>)</code>.  If
  <var>i</var> is greater than or equal to <var>j</var>, the slice is empty.

<P>
</DD>
<DT><STRONG>(5)</STRONG></DT>
<DD>The slice of <var>s</var> from <var>i</var> to <var>j</var> with step
  <var>k</var> is defined as the sequence of items with index 
  <code><var>x</var> = <var>i</var> + <var>n</var>*<var>k</var></code> such that
  <!-- MATH
 $0 \leq n < \frac{j-i}{k}$
 -->
<SPAN CLASS="MATH"><IMG
 WIDTH="88" HEIGHT="37" ALIGN="MIDDLE" BORDER="0"
 SRC="img1.png"
 ALT="$0 \leq n &lt; \frac{j-i}{k}$"></SPAN>.  In other words, the indices
  are <code>i</code>, <code>i+k</code>, <code>i+2*k</code>, <code>i+3*k</code> and so on, stopping when
  <var>j</var> is reached (but never including <var>j</var>).  If <var>i</var> or <var>j</var>
  is greater than <code>len(<var>s</var>)</code>, use <code>len(<var>s</var>)</code>.  If
  <var>i</var> or <var>j</var> are omitted then they become ``end'' values
  (which end depends on the sign of <var>k</var>).  Note, <var>k</var> cannot
  be zero.

<P>
</DD>
<DT><STRONG>(6)</STRONG></DT>
<DD>If <var>s</var> and <var>t</var> are both strings, some Python
implementations such as CPython can usually perform an in-place optimization
for assignments of the form <code><var>s</var>=<var>s</var>+<var>t</var></code> or
<code><var>s</var>+=<var>t</var></code>.  When applicable, this optimization makes
quadratic run-time much less likely.  This optimization is both version
and implementation dependent.  For performance sensitive code, it is
preferable to use the <tt class="method">str.join()</tt> method which assures consistent
linear concatenation performance across versions and implementations.

<span class="versionnote">Changed in version 2.4:
Formerly, string concatenation never occurred in-place.</span>

<P>
</DD>
</DL>

<P>
<BR><HR><H4>Footnotes</H4>
<DL>
<DT><A NAME="foot1961">... operations.</A><A
 href="typesseq.html#tex2html8"><SUP>2.7</SUP></A></DT>
<DD>They must
have since the parser can't tell the type of the operands.

</DD>
</DL>
<p><br /></p><hr class='online-navigation' />
<div class='online-navigation'>
<!--Table of Child-Links-->
<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a>

<UL CLASS="ChildLinks">
<LI><A href="string-methods.html">2.3.6.1 String Methods</a>
<LI><A href="typesseq-strings.html">2.3.6.2 String Formatting Operations</a>
<LI><A href="typesseq-xrange.html">2.3.6.3 XRange Type</a>
<LI><A href="typesseq-mutable.html">2.3.6.4 Mutable Sequence Types</a>
</ul>
<!--End of Table of Child-Links-->
</div>

<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="2.3.5 Iterator Types"
  href="typeiter.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="2.3 Built-in Types"
  href="types.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="2.3.6.1 String Methods"
  href="string-methods.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="typeiter.html">2.3.5 Iterator Types</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="types.html">2.3 Built-in Types</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="string-methods.html">2.3.6.1 String Methods</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>
Commit	Line	Data
920dae64 AT	1	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
	2	<html>
	3	<head>
	4	<link rel="STYLESHEET" href="lib.css" type='text/css' />
	5	<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
	6	<link rel='start' href='../index.html' title='Python Documentation Index' />
	7	<link rel="first" href="lib.html" title='Python Library Reference' />
	8	<link rel='contents' href='contents.html' title="Contents" />
	9	<link rel='index' href='genindex.html' title='Index' />
	10	<link rel='last' href='about.html' title='About this document...' />
	11	<link rel='help' href='about.html' title='About this document...' />
	12	<link rel="next" href="types-set.html" />
	13	<link rel="prev" href="typeiter.html" />
	14	<link rel="parent" href="types.html" />
	15	<link rel="next" href="string-methods.html" />
	16	<meta name='aesop' content='information' />
	17	<title>2.3.6 Sequence Types -- str, unicode, list, tuple, buffer, xrange </title>
	18	</head>
	19	<body>
	20	<DIV CLASS="navigation">
	21	<div id='top-navigation-panel' xml:id='top-navigation-panel'>
	22	<table align="center" width="100%" cellpadding="0" cellspacing="2">
	23	<tr>
	24	<td class='online-navigation'><a rel="prev" title="2.3.5 Iterator Types"
	25	href="typeiter.html"><img src='../icons/previous.png'
	26	border='0' height='32' alt='Previous Page' width='32' /></A></td>
	27	<td class='online-navigation'><a rel="parent" title="2.3 Built-in Types"
	28	href="types.html"><img src='../icons/up.png'
	29	border='0' height='32' alt='Up One Level' width='32' /></A></td>
	30	<td class='online-navigation'><a rel="next" title="2.3.6.1 String Methods"
	31	href="string-methods.html"><img src='../icons/next.png'
	32	border='0' height='32' alt='Next Page' width='32' /></A></td>
	33	<td align="center" width="100%">Python Library Reference</td>
	34	<td class='online-navigation'><a rel="contents" title="Table of Contents"
	35	href="contents.html"><img src='../icons/contents.png'
	36	border='0' height='32' alt='Contents' width='32' /></A></td>
	37	<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
	38	border='0' height='32' alt='Module Index' width='32' /></a></td>
	39	<td class='online-navigation'><a rel="index" title="Index"
	40	href="genindex.html"><img src='../icons/index.png'
	41	border='0' height='32' alt='Index' width='32' /></A></td>
	42	</tr></table>
	43	<div class='online-navigation'>
	44	<b class="navlabel">Previous:</b>
	45	<a class="sectref" rel="prev" href="typeiter.html">2.3.5 Iterator Types</A>
	46	<b class="navlabel">Up:</b>
	47	<a class="sectref" rel="parent" href="types.html">2.3 Built-in Types</A>
	48	<b class="navlabel">Next:</b>
	49	<a class="sectref" rel="next" href="string-methods.html">2.3.6.1 String Methods</A>
	50	</div>
	51	<hr /></div>
	52	</DIV>
	53	<!--End of Navigation Panel-->
	54
	55	<H2><A NAME="SECTION004360000000000000000"></A><A NAME="typesseq"></A>
	56	<BR>
	57	2.3.6 Sequence Types --
	58	<tt class="class">str</tt>, <tt class="class">unicode</tt>, <tt class="class">list</tt>,
	59	<tt class="class">tuple</tt>, <tt class="class">buffer</tt>, <tt class="class">xrange</tt>
	60
	61	</H2>
	62
	63	<P>
	64	There are six sequence types: strings, Unicode strings, lists,
65	tuples, buffers, and xrange objects.
66
67	<P>
68	String literals are written in single or double quotes:
69	<code>'xyzzy'</code>, <code>"frobozz"</code>. See chapter 2 of the
70	<em class="citetitle"><a
71	href="../ref/strings.html"
72	title="Python Reference Manual"
73	>Python Reference Manual</a></em> for more about
74	string literals. Unicode strings are much like strings, but are
75	specified in the syntax using a preceding "<tt class="character">u</tt>" character:
76	<code>u'abc'</code>, <code>u"def"</code>. Lists are constructed with square brackets,
77	separating items with commas: <code>[a, b, c]</code>. Tuples are
78	constructed by the comma operator (not within square brackets), with
79	or without enclosing parentheses, but an empty tuple must have the
80	enclosing parentheses, such as <code>a, b, c</code> or <code>()</code>. A single
81	item tuple must have a trailing comma, such as <code>(d,)</code>.
82	<a id='l2h-156' xml:id='l2h-156'></a><a id='l2h-157' xml:id='l2h-157'></a><a id='l2h-158' xml:id='l2h-158'></a><a id='l2h-159' xml:id='l2h-159'></a><a id='l2h-160' xml:id='l2h-160'></a>
83	<P>
84	Buffer objects are not directly supported by Python syntax, but can be
85	created by calling the builtin function
86	<tt class="function">buffer()</tt>.<a id='l2h-161' xml:id='l2h-161'></a> They don't support
87	concatenation or repetition.
88	<a id='l2h-162' xml:id='l2h-162'></a>
89	<P>
90	Xrange objects are similar to buffers in that there is no specific
91	syntax to create them, but they are created using the <tt class="function">xrange()</tt>
92	function.<a id='l2h-163' xml:id='l2h-163'></a> They don't support slicing,
93	concatenation or repetition, and using <code>in</code>, <code>not in</code>,
94	<tt class="function">min()</tt> or <tt class="function">max()</tt> on them is inefficient.
95	<a id='l2h-164' xml:id='l2h-164'></a>
96	<P>
97	Most sequence types support the following operations. The "<tt class="samp">in</tt>" and
98	"<tt class="samp">not in</tt>" operations have the same priorities as the comparison
99	operations. The "<tt class="samp">+</tt>" and "<tt class="samp">*</tt>" operations have the same
100	priority as the corresponding numeric operations.<A NAME="tex2html8"
101	HREF="#foot1961"><SUP>2.7</SUP></A>
102	<P>
103	This table lists the sequence operations sorted in ascending priority
104	(operations in the same box have the same priority). In the table,
105	<var>s</var> and <var>t</var> are sequences of the same type; <var>n</var>, <var>i</var>
106	and <var>j</var> are integers:
107
108	<P>
109	<div class="center"><table class="realtable">
110	<thead>
111	<tr>
112	<th class="center">Operation</th>
113	<th class="left" >Result</th>
114	<th class="center">Notes</th>
115	</tr>
116	</thead>
117	<tbody>
118	<tr><td class="center" valign="baseline"><code><var>x</var> in <var>s</var></code></td>
119	<td class="left" ><code>True</code> if an item of <var>s</var> is equal to <var>x</var>, else <code>False</code></td>
120	<td class="center">(1)</td></tr>
121	<tr><td class="center" valign="baseline"><code><var>x</var> not in <var>s</var></code></td>
122	<td class="left" ><code>False</code> if an item of <var>s</var> is
123	equal to <var>x</var>, else <code>True</code></td>
124	<td class="center">(1)</td></tr>
125
126	<tr><td class="center" valign="baseline"><code><var>s</var> + <var>t</var></code></td>
127	<td class="left" >the concatenation of <var>s</var> and <var>t</var></td>
128	<td class="center">(6)</td></tr>
129	<tr><td class="center" valign="baseline"><code><var>s</var> * <var>n</var> , <var>n</var> * <var>s</var></code></td>
130	<td class="left" ><var>n</var> shallow copies of <var>s</var> concatenated</td>
131	<td class="center">(2)</td></tr>
132
133	<tr><td class="center" valign="baseline"><code><var>s</var>[<var>i</var>]</code></td>
134	<td class="left" ><var>i</var>'th item of <var>s</var>, origin 0</td>
135	<td class="center">(3)</td></tr>
136	<tr><td class="center" valign="baseline"><code><var>s</var>[<var>i</var>:<var>j</var>]</code></td>
137	<td class="left" >slice of <var>s</var> from <var>i</var> to <var>j</var></td>
138	<td class="center">(3), (4)</td></tr>
139	<tr><td class="center" valign="baseline"><code><var>s</var>[<var>i</var>:<var>j</var>:<var>k</var>]</code></td>
140	<td class="left" >slice of <var>s</var> from <var>i</var> to <var>j</var> with step <var>k</var></td>
141	<td class="center">(3), (5)</td></tr>
142
143	<tr><td class="center" valign="baseline"><code>len(<var>s</var>)</code></td>
144	<td class="left" >length of <var>s</var></td>
145	<td class="center"></td></tr>
146	<tr><td class="center" valign="baseline"><code>min(<var>s</var>)</code></td>
147	<td class="left" >smallest item of <var>s</var></td>
148	<td class="center"></td></tr>
149	<tr><td class="center" valign="baseline"><code>max(<var>s</var>)</code></td>
150	<td class="left" >largest item of <var>s</var></td>
151	<td class="center"></td></tr></tbody>
152	</table></div>
153	<a id='l2h-165' xml:id='l2h-165'></a><a id='l2h-166' xml:id='l2h-166'></a><a id='l2h-167' xml:id='l2h-167'></a><a id='l2h-168' xml:id='l2h-168'></a><a id='l2h-169' xml:id='l2h-169'></a><a id='l2h-170' xml:id='l2h-170'></a><a id='l2h-171' xml:id='l2h-171'></a><a id='l2h-172' xml:id='l2h-172'></a><a id='l2h-173' xml:id='l2h-173'></a><a id='l2h-174' xml:id='l2h-174'></a><a id='l2h-175' xml:id='l2h-175'></a>
154	<P>
155	Notes:
156
157	<P>
158	<DL>
159	<DT><STRONG>(1)</STRONG></DT>
160	<DD>When <var>s</var> is a string or Unicode string object the
161	<code>in</code> and <code>not in</code> operations act like a substring test. In
162	Python versions before 2.3, <var>x</var> had to be a string of length 1.
163	In Python 2.3 and beyond, <var>x</var> may be a string of any length.
164
165	<P>
166	</DD>
167	<DT><STRONG>(2)</STRONG></DT>
168	<DD>Values of <var>n</var> less than <code>0</code> are treated as
169	<code>0</code> (which yields an empty sequence of the same type as
170	<var>s</var>). Note also that the copies are shallow; nested structures
171	are not copied. This often haunts new Python programmers; consider:
172
173	<P>
174	<div class="verbatim"><pre>
175	>>> lists = [[]] * 3
176	>>> lists
177	[[], [], []]
178	>>> lists[0].append(3)
179	>>> lists
180	[[3], [3], [3]]
181	</pre></div>
182
183	<P>
184	What has happened is that <code>[[]]</code> is a one-element list containing
185	an empty list, so all three elements of <code>[[]] * 3</code> are (pointers to)
186	this single empty list. Modifying any of the elements of <code>lists</code>
187	modifies this single list. You can create a list of different lists this
188	way:
189
190	<P>
191	<div class="verbatim"><pre>
192	>>> lists = [[] for i in range(3)]
193	>>> lists[0].append(3)
194	>>> lists[1].append(5)
195	>>> lists[2].append(7)
196	>>> lists
197	[[3], [5], [7]]
198	</pre></div>
199
200	<P>
201	</DD>
202	<DT><STRONG>(3)</STRONG></DT>
203	<DD>If <var>i</var> or <var>j</var> is negative, the index is relative to
204	the end of the string: <code>len(<var>s</var>) + <var>i</var></code> or
205	<code>len(<var>s</var>) + <var>j</var></code> is substituted. But note that <code>-0</code> is
206	still <code>0</code>.
207
208	<P>
209	</DD>
210	<DT><STRONG>(4)</STRONG></DT>
211	<DD>The slice of <var>s</var> from <var>i</var> to <var>j</var> is defined as
212	the sequence of items with index <var>k</var> such that <code><var>i</var> <=
213	<var>k</var> < <var>j</var></code>. If <var>i</var> or <var>j</var> is greater than
214	<code>len(<var>s</var>)</code>, use <code>len(<var>s</var>)</code>. If <var>i</var> is omitted,
215	use <code>0</code>. If <var>j</var> is omitted, use <code>len(<var>s</var>)</code>. If
216	<var>i</var> is greater than or equal to <var>j</var>, the slice is empty.
217
218	<P>
219	</DD>
220	<DT><STRONG>(5)</STRONG></DT>
221	<DD>The slice of <var>s</var> from <var>i</var> to <var>j</var> with step
222	<var>k</var> is defined as the sequence of items with index
223	<code><var>x</var> = <var>i</var> + <var>n</var>*<var>k</var></code> such that
224	<!-- MATH
225	$0 \leq n < \frac{j-i}{k}$
226	-->
227	<SPAN CLASS="MATH"><IMG
228	WIDTH="88" HEIGHT="37" ALIGN="MIDDLE" BORDER="0"
229	SRC="img1.png"
230	ALT="$0 \leq n < \frac{j-i}{k}$"></SPAN>. In other words, the indices
231	are <code>i</code>, <code>i+k</code>, <code>i+2k</code>, <code>i+3k</code> and so on, stopping when
232	<var>j</var> is reached (but never including <var>j</var>). If <var>i</var> or <var>j</var>
233	is greater than <code>len(<var>s</var>)</code>, use <code>len(<var>s</var>)</code>. If
234	<var>i</var> or <var>j</var> are omitted then they become ``end'' values
235	(which end depends on the sign of <var>k</var>). Note, <var>k</var> cannot
236	be zero.
237
238	<P>
239	</DD>
240	<DT><STRONG>(6)</STRONG></DT>
241	<DD>If <var>s</var> and <var>t</var> are both strings, some Python
242	implementations such as CPython can usually perform an in-place optimization
243	for assignments of the form <code><var>s</var>=<var>s</var>+<var>t</var></code> or
244	<code><var>s</var>+=<var>t</var></code>. When applicable, this optimization makes
245	quadratic run-time much less likely. This optimization is both version
246	and implementation dependent. For performance sensitive code, it is
247	preferable to use the <tt class="method">str.join()</tt> method which assures consistent
248	linear concatenation performance across versions and implementations.
249
250	<span class="versionnote">Changed in version 2.4:
251	Formerly, string concatenation never occurred in-place.</span>
252
253	<P>
254	</DD>
255	</DL>
256
257	<P>
258	<BR><HR><H4>Footnotes</H4>
259	<DL>
260	<DT><A NAME="foot1961">... operations.</A><A
261	href="typesseq.html#tex2html8"><SUP>2.7</SUP></A></DT>
262	<DD>They must
263	have since the parser can't tell the type of the operands.
264
265	</DD>
266	</DL>
267	<p><br /></p><hr class='online-navigation' />
268	<div class='online-navigation'>
269	<!--Table of Child-Links-->
270	<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a>
271
272	<UL CLASS="ChildLinks">
273	<LI><A href="string-methods.html">2.3.6.1 String Methods</a>
274	<LI><A href="typesseq-strings.html">2.3.6.2 String Formatting Operations</a>
275	<LI><A href="typesseq-xrange.html">2.3.6.3 XRange Type</a>
276	<LI><A href="typesseq-mutable.html">2.3.6.4 Mutable Sequence Types</a>
277	</ul>
278	<!--End of Table of Child-Links-->
279	</div>
280
281	<DIV CLASS="navigation">
282	<div class='online-navigation'>
283	<p></p><hr />
284	<table align="center" width="100%" cellpadding="0" cellspacing="2">
285	<tr>
286	<td class='online-navigation'><a rel="prev" title="2.3.5 Iterator Types"
287	href="typeiter.html"><img src='../icons/previous.png'
288	border='0' height='32' alt='Previous Page' width='32' /></A></td>
289	<td class='online-navigation'><a rel="parent" title="2.3 Built-in Types"
290	href="types.html"><img src='../icons/up.png'
291	border='0' height='32' alt='Up One Level' width='32' /></A></td>
292	<td class='online-navigation'><a rel="next" title="2.3.6.1 String Methods"
293	href="string-methods.html"><img src='../icons/next.png'
294	border='0' height='32' alt='Next Page' width='32' /></A></td>
295	<td align="center" width="100%">Python Library Reference</td>
296	<td class='online-navigation'><a rel="contents" title="Table of Contents"
297	href="contents.html"><img src='../icons/contents.png'
298	border='0' height='32' alt='Contents' width='32' /></A></td>
299	<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
300	border='0' height='32' alt='Module Index' width='32' /></a></td>
301	<td class='online-navigation'><a rel="index" title="Index"
302	href="genindex.html"><img src='../icons/index.png'
303	border='0' height='32' alt='Index' width='32' /></A></td>
304	</tr></table>
305	<div class='online-navigation'>
306	<b class="navlabel">Previous:</b>
307	<a class="sectref" rel="prev" href="typeiter.html">2.3.5 Iterator Types</A>
308	<b class="navlabel">Up:</b>
309	<a class="sectref" rel="parent" href="types.html">2.3 Built-in Types</A>
310	<b class="navlabel">Next:</b>
311	<a class="sectref" rel="next" href="string-methods.html">2.3.6.1 String Methods</A>
312	</div>
313	</div>
314	<hr />
315	<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
316	</DIV>
317	<!--End of Navigation Panel-->
318	<ADDRESS>
319	See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
320	</ADDRESS>
321	</BODY>
322	</HTML>