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<H2><A NAME="SECTION004410000000000000000"></A><A NAME="strings"></A><a id='l2h-13' xml:id='l2h-13'></a>
<BR>
2.4.1 String literals
</H2>

<P>
String literals are described by the following lexical definitions:

<P>

<dl><dd class="grammar">
<div class="productions">
<table>
<tr>
    <td><a id='tok-stringliteral' xml:id='tok-stringliteral'>stringliteral</a></td>
    <td>::=</td>
    <td>[<a class='grammartoken' href="strings.html#tok-stringprefix">stringprefix</a>](<a class='grammartoken' href="strings.html#tok-shortstring">shortstring</a> | <a class='grammartoken' href="strings.html#tok-longstring">longstring</a>)</td></tr>
  <tr>
    <td><a id='tok-stringprefix' xml:id='tok-stringprefix'>stringprefix</a></td>
    <td>::=</td>
    <td>"r" | "u" | "ur" | "R" | "U" | "UR" | "Ur" | "uR"</td></tr>
  <tr>
    <td><a id='tok-shortstring' xml:id='tok-shortstring'>shortstring</a></td>
    <td>::=</td>
    <td>"'" <a class='grammartoken' href="strings.html#tok-shortstringitem">shortstringitem</a>* "'"
              | '"' <a class='grammartoken' href="strings.html#tok-shortstringitem">shortstringitem</a>* '"'</td></tr>
  <tr>
    <td><a id='tok-longstring' xml:id='tok-longstring'>longstring</a></td>
    <td>::=</td>
    <td>"'''" <a class='grammartoken' href="strings.html#tok-longstringitem">longstringitem</a>* "'''"</td></tr>
  <tr>
    <td></td>
    <td></td>
    <td><code>| '"""' <a class='grammartoken' href="strings.html#tok-longstringitem">longstringitem</a>* '"""'</code></td></tr>
  <tr>
    <td><a id='tok-shortstringitem' xml:id='tok-shortstringitem'>shortstringitem</a></td>
    <td>::=</td>
    <td><a class='grammartoken' href="strings.html#tok-shortstringchar">shortstringchar</a> | <a class='grammartoken' href="strings.html#tok-escapeseq">escapeseq</a></td></tr>
  <tr>
    <td><a id='tok-longstringitem' xml:id='tok-longstringitem'>longstringitem</a></td>
    <td>::=</td>
    <td><a class='grammartoken' href="strings.html#tok-longstringchar">longstringchar</a> | <a class='grammartoken' href="strings.html#tok-escapeseq">escapeseq</a></td></tr>
  <tr>
    <td><a id='tok-shortstringchar' xml:id='tok-shortstringchar'>shortstringchar</a></td>
    <td>::=</td>
    <td>&lt;any source character except "&#92;" or newline or the quote&gt;</td></tr>
  <tr>
    <td><a id='tok-longstringchar' xml:id='tok-longstringchar'>longstringchar</a></td>
    <td>::=</td>
    <td>&lt;any source character except "&#92;"&gt;</td></tr>
  <tr>
    <td><a id='tok-escapeseq' xml:id='tok-escapeseq'>escapeseq</a></td>
    <td>::=</td>
    <td>"&#92;" &lt;any ASCII character&gt;</td></tr>
</table>
</div>
<a class="grammar-footer"
  href="grammar.txt" type="text/plain"
  >Download entire grammar as text.</a>
</dd></dl>

<P>
One syntactic restriction not indicated by these productions is that
whitespace is not allowed between the <a class='grammartoken' href="strings.html#tok-stringprefix">stringprefix</a> and
the rest of the string literal. The source character set is defined
by the encoding declaration; it is ASCII if no encoding declaration
is given in the source file; see section&nbsp;<A href="encodings.html#encodings">2.1.4</A>.

<P>
In plain English: String literals can be enclosed in matching single
quotes (<code>'</code>) or double quotes (<code>"</code>).  They can also be
enclosed in matching groups of three single or double quotes (these
are generally referred to as <em>triple-quoted strings</em>).  The
backslash (<code>&#92;</code>) character is used to escape characters that
otherwise have a special meaning, such as newline, backslash itself,
or the quote character.  String literals may optionally be prefixed
with a letter "<tt class="character">r</tt>" or "<tt class="character">R</tt>"; such strings are called
<i class="dfn">raw strings</i><a id='l2h-14' xml:id='l2h-14'></a> and use different rules for interpreting
backslash escape sequences.  A prefix of "<tt class="character">u</tt>" or "<tt class="character">U</tt>"
makes the string a Unicode string.  Unicode strings use the Unicode character
set as defined by the Unicode Consortium and ISO&nbsp;10646.  Some additional
escape sequences, described below, are available in Unicode strings.
The two prefix characters may be combined; in this case, "<tt class="character">u</tt>" must
appear before "<tt class="character">r</tt>".

<P>
In triple-quoted strings,
unescaped newlines and quotes are allowed (and are retained), except
that three unescaped quotes in a row terminate the string.  (A
``quote'' is the character used to open the string, i.e. either
<code>'</code> or <code>"</code>.)

<P>
Unless an "<tt class="character">r</tt>" or "<tt class="character">R</tt>" prefix is present, escape
sequences in strings are interpreted according to rules similar
to those used by Standard C.  The recognized escape sequences are:

<P>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="left"  >Escape Sequence</th>
      <th class="left"  >Meaning</th>
      <th class="center">Notes</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="left"   valign="baseline"><code>&#92;<var>newline</var></code></td>
        <td class="left"  >Ignored</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;&#92;</code></td>
        <td class="left"  >Backslash (<code>&#92;</code>)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;'</code></td>
        <td class="left"  >Single quote (<code>'</code>)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;"</code></td>
        <td class="left"  >Double quote (<code>"</code>)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;a</code></td>
        <td class="left"  >ASCII Bell (BEL)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;b</code></td>
        <td class="left"  >ASCII Backspace (BS)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;f</code></td>
        <td class="left"  >ASCII Formfeed (FF)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;n</code></td>
        <td class="left"  >ASCII Linefeed (LF)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;N{<var>name</var>}</code></td>
        <td class="left"  >Character named <var>name</var> in the Unicode database (Unicode only)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;r</code></td>
        <td class="left"  >ASCII Carriage Return (CR)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;t</code></td>
        <td class="left"  >ASCII Horizontal Tab (TAB)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;u<var>xxxx</var></code></td>
        <td class="left"  >Character with 16-bit hex value <var>xxxx</var> (Unicode only)</td>
        <td class="center">(1)</td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;U<var>xxxxxxxx</var></code></td>
        <td class="left"  >Character with 32-bit hex value <var>xxxxxxxx</var> (Unicode only)</td>
        <td class="center">(2)</td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;v</code></td>
        <td class="left"  >ASCII Vertical Tab (VT)</td>
        <td class="center"></td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;<var>ooo</var></code></td>
        <td class="left"  >Character with octal value <var>ooo</var></td>
        <td class="center">(3,5)</td></tr>
    <tr><td class="left"   valign="baseline"><code>&#92;x<var>hh</var></code></td>
        <td class="left"  >Character with hex value <var>hh</var></td>
        <td class="center">(4,5)</td></tr></tbody>
</table></div>

<P>
Notes:

<P>
<DL COMPACT>
<DT>(1)</DT>
<DD>Individual code units which form parts of a surrogate pair can be
  encoded using this escape sequence.
</DD>
<DT>(2)</DT>
<DD>Any Unicode character can be encoded this way, but characters
  outside the Basic Multilingual Plane (BMP) will be encoded using a
  surrogate pair if Python is compiled to use 16-bit code units (the
  default).  Individual code units which form parts of a surrogate
  pair can be encoded using this escape sequence.
</DD>
<DT>(3)</DT>
<DD>As in Standard C, up to three octal digits are accepted.
</DD>
<DT>(4)</DT>
<DD>Unlike in Standard C, at most two hex digits are accepted.
</DD>
<DT>(5)</DT>
<DD>In a string literal, hexadecimal and octal escapes denote the
  byte with the given value; it is not necessary that the byte
  encodes a character in the source character set. In a Unicode
  literal, these escapes denote a Unicode character with the given
  value.
</DD>
</DL>

<P>
Unlike Standard <a id='l2h-15' xml:id='l2h-15'></a>C,
all unrecognized escape sequences are left in the string unchanged,
i.e., <em>the backslash is left in the string</em>.  (This behavior is
useful when debugging: if an escape sequence is mistyped, the
resulting output is more easily recognized as broken.)  It is also
important to note that the escape sequences marked as ``(Unicode
only)'' in the table above fall into the category of unrecognized
escapes for non-Unicode string literals.

<P>
When an "<tt class="character">r</tt>" or "<tt class="character">R</tt>" prefix is present, a character
following a backslash is included in the string without change, and <em>all
backslashes are left in the string</em>.  For example, the string literal
<code>r"&#92;n"</code> consists of two characters: a backslash and a lowercase
"<tt class="character">n</tt>".  String quotes can be escaped with a backslash, but the
backslash remains in the string; for example, <code>r"&#92;""</code> is a valid string
literal consisting of two characters: a backslash and a double quote;
<code>r"&#92;"</code> is not a valid string literal (even a raw string cannot
end in an odd number of backslashes).  Specifically, <em>a raw
string cannot end in a single backslash</em> (since the backslash would
escape the following quote character).  Note also that a single
backslash followed by a newline is interpreted as those two characters
as part of the string, <em>not</em> as a line continuation.

<P>
When an "<tt class="character">r</tt>" or "<tt class="character">R</tt>" prefix is used in conjunction
with a "<tt class="character">u</tt>" or "<tt class="character">U</tt>" prefix, then the <code>&#92;uXXXX</code>
escape sequence is processed while <em>all other backslashes are
left in the string</em>.  For example, the string literal
<code>ur"&#92;u0062&#92;n"</code> consists of three Unicode characters: `LATIN
SMALL LETTER B', `REVERSE SOLIDUS', and `LATIN SMALL LETTER N'.
Backslashes can be escaped with a preceding backslash; however, both
remain in the string.  As a result, <code>&#92;uXXXX</code> escape sequences
are only recognized when there are an odd number of backslashes.

<P>

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	54
	55	<H2><A NAME="SECTION004410000000000000000"></A><A NAME="strings"></A><a id='l2h-13' xml:id='l2h-13'></a>
	56	<BR>
	57	2.4.1 String literals
	58	</H2>
	59
	60	<P>
	61	String literals are described by the following lexical definitions:
	62
	63	<P>
	64
65	<dl><dd class="grammar">
66	<div class="productions">
67	<table>
68	<tr>
69	<td><a id='tok-stringliteral' xml:id='tok-stringliteral'>stringliteral</a></td>
70	<td>::=</td>
71	<td>[<a class='grammartoken' href="strings.html#tok-stringprefix">stringprefix</a>](<a class='grammartoken' href="strings.html#tok-shortstring">shortstring</a> \| <a class='grammartoken' href="strings.html#tok-longstring">longstring</a>)</td></tr>
72	<tr>
73	<td><a id='tok-stringprefix' xml:id='tok-stringprefix'>stringprefix</a></td>
74	<td>::=</td>
75	<td>"r" \| "u" \| "ur" \| "R" \| "U" \| "UR" \| "Ur" \| "uR"</td></tr>
76	<tr>
77	<td><a id='tok-shortstring' xml:id='tok-shortstring'>shortstring</a></td>
78	<td>::=</td>
79	<td>"'" <a class='grammartoken' href="strings.html#tok-shortstringitem">shortstringitem</a>* "'"
80	\| '"' <a class='grammartoken' href="strings.html#tok-shortstringitem">shortstringitem</a>* '"'</td></tr>
81	<tr>
82	<td><a id='tok-longstring' xml:id='tok-longstring'>longstring</a></td>
83	<td>::=</td>
84	<td>"'''" <a class='grammartoken' href="strings.html#tok-longstringitem">longstringitem</a>* "'''"</td></tr>
85	<tr>
86	<td></td>
87	<td></td>
88	<td><code>\| '"""' <a class='grammartoken' href="strings.html#tok-longstringitem">longstringitem</a>* '"""'</code></td></tr>
89	<tr>
90	<td><a id='tok-shortstringitem' xml:id='tok-shortstringitem'>shortstringitem</a></td>
91	<td>::=</td>
92	<td><a class='grammartoken' href="strings.html#tok-shortstringchar">shortstringchar</a> \| <a class='grammartoken' href="strings.html#tok-escapeseq">escapeseq</a></td></tr>
93	<tr>
94	<td><a id='tok-longstringitem' xml:id='tok-longstringitem'>longstringitem</a></td>
95	<td>::=</td>
96	<td><a class='grammartoken' href="strings.html#tok-longstringchar">longstringchar</a> \| <a class='grammartoken' href="strings.html#tok-escapeseq">escapeseq</a></td></tr>
97	<tr>
98	<td><a id='tok-shortstringchar' xml:id='tok-shortstringchar'>shortstringchar</a></td>
99	<td>::=</td>
100	<td><any source character except "\" or newline or the quote></td></tr>
101	<tr>
102	<td><a id='tok-longstringchar' xml:id='tok-longstringchar'>longstringchar</a></td>
103	<td>::=</td>
104	<td><any source character except "\"></td></tr>
105	<tr>
106	<td><a id='tok-escapeseq' xml:id='tok-escapeseq'>escapeseq</a></td>
107	<td>::=</td>
108	<td>"\" <any ASCII character></td></tr>
109	</table>
110	</div>
111	<a class="grammar-footer"
112	href="grammar.txt" type="text/plain"
113	>Download entire grammar as text.</a>
114	</dd></dl>
115
116	<P>
117	One syntactic restriction not indicated by these productions is that
118	whitespace is not allowed between the <a class='grammartoken' href="strings.html#tok-stringprefix">stringprefix</a> and
119	the rest of the string literal. The source character set is defined
120	by the encoding declaration; it is ASCII if no encoding declaration
121	is given in the source file; see section <A href="encodings.html#encodings">2.1.4</A>.
122
123	<P>
124	In plain English: String literals can be enclosed in matching single
125	quotes (<code>'</code>) or double quotes (<code>"</code>). They can also be
126	enclosed in matching groups of three single or double quotes (these
127	are generally referred to as <em>triple-quoted strings</em>). The
128	backslash (<code>\</code>) character is used to escape characters that
129	otherwise have a special meaning, such as newline, backslash itself,
130	or the quote character. String literals may optionally be prefixed
131	with a letter "<tt class="character">r</tt>" or "<tt class="character">R</tt>"; such strings are called
132	<i class="dfn">raw strings</i><a id='l2h-14' xml:id='l2h-14'></a> and use different rules for interpreting
133	backslash escape sequences. A prefix of "<tt class="character">u</tt>" or "<tt class="character">U</tt>"
134	makes the string a Unicode string. Unicode strings use the Unicode character
135	set as defined by the Unicode Consortium and ISO 10646. Some additional
136	escape sequences, described below, are available in Unicode strings.
137	The two prefix characters may be combined; in this case, "<tt class="character">u</tt>" must
138	appear before "<tt class="character">r</tt>".
139
140	<P>
141	In triple-quoted strings,
142	unescaped newlines and quotes are allowed (and are retained), except
143	that three unescaped quotes in a row terminate the string. (A
144	``quote'' is the character used to open the string, i.e. either
145	<code>'</code> or <code>"</code>.)
146
147	<P>
148	Unless an "<tt class="character">r</tt>" or "<tt class="character">R</tt>" prefix is present, escape
149	sequences in strings are interpreted according to rules similar
150	to those used by Standard C. The recognized escape sequences are:
151
152	<P>
153	<div class="center"><table class="realtable">
154	<thead>
155	<tr>
156	<th class="left" >Escape Sequence</th>
157	<th class="left" >Meaning</th>
158	<th class="center">Notes</th>
159	</tr>
160	</thead>
161	<tbody>
162	<tr><td class="left" valign="baseline"><code>\<var>newline</var></code></td>
163	<td class="left" >Ignored</td>
164	<td class="center"></td></tr>
165	<tr><td class="left" valign="baseline"><code>\\</code></td>
166	<td class="left" >Backslash (<code>\</code>)</td>
167	<td class="center"></td></tr>
168	<tr><td class="left" valign="baseline"><code>\'</code></td>
169	<td class="left" >Single quote (<code>'</code>)</td>
170	<td class="center"></td></tr>
171	<tr><td class="left" valign="baseline"><code>\"</code></td>
172	<td class="left" >Double quote (<code>"</code>)</td>
173	<td class="center"></td></tr>
174	<tr><td class="left" valign="baseline"><code>\a</code></td>
175	<td class="left" >ASCII Bell (BEL)</td>
176	<td class="center"></td></tr>
177	<tr><td class="left" valign="baseline"><code>\b</code></td>
178	<td class="left" >ASCII Backspace (BS)</td>
179	<td class="center"></td></tr>
180	<tr><td class="left" valign="baseline"><code>\f</code></td>
181	<td class="left" >ASCII Formfeed (FF)</td>
182	<td class="center"></td></tr>
183	<tr><td class="left" valign="baseline"><code>\n</code></td>
184	<td class="left" >ASCII Linefeed (LF)</td>
185	<td class="center"></td></tr>
186	<tr><td class="left" valign="baseline"><code>\N{<var>name</var>}</code></td>
187	<td class="left" >Character named <var>name</var> in the Unicode database (Unicode only)</td>
188	<td class="center"></td></tr>
189	<tr><td class="left" valign="baseline"><code>\r</code></td>
190	<td class="left" >ASCII Carriage Return (CR)</td>
191	<td class="center"></td></tr>
192	<tr><td class="left" valign="baseline"><code>\t</code></td>
193	<td class="left" >ASCII Horizontal Tab (TAB)</td>
194	<td class="center"></td></tr>
195	<tr><td class="left" valign="baseline"><code>\u<var>xxxx</var></code></td>
196	<td class="left" >Character with 16-bit hex value <var>xxxx</var> (Unicode only)</td>
197	<td class="center">(1)</td></tr>
198	<tr><td class="left" valign="baseline"><code>\U<var>xxxxxxxx</var></code></td>
199	<td class="left" >Character with 32-bit hex value <var>xxxxxxxx</var> (Unicode only)</td>
200	<td class="center">(2)</td></tr>
201	<tr><td class="left" valign="baseline"><code>\v</code></td>
202	<td class="left" >ASCII Vertical Tab (VT)</td>
203	<td class="center"></td></tr>
204	<tr><td class="left" valign="baseline"><code>\<var>ooo</var></code></td>
205	<td class="left" >Character with octal value <var>ooo</var></td>
206	<td class="center">(3,5)</td></tr>
207	<tr><td class="left" valign="baseline"><code>\x<var>hh</var></code></td>
208	<td class="left" >Character with hex value <var>hh</var></td>
209	<td class="center">(4,5)</td></tr></tbody>
210	</table></div>
211
212	<P>
213	Notes:
214
215	<P>
216	<DL COMPACT>
217	<DT>(1)</DT>
218	<DD>Individual code units which form parts of a surrogate pair can be
219	encoded using this escape sequence.
220	</DD>
221	<DT>(2)</DT>
222	<DD>Any Unicode character can be encoded this way, but characters
223	outside the Basic Multilingual Plane (BMP) will be encoded using a
224	surrogate pair if Python is compiled to use 16-bit code units (the
225	default). Individual code units which form parts of a surrogate
226	pair can be encoded using this escape sequence.
227	</DD>
228	<DT>(3)</DT>
229	<DD>As in Standard C, up to three octal digits are accepted.
230	</DD>
231	<DT>(4)</DT>
232	<DD>Unlike in Standard C, at most two hex digits are accepted.
233	</DD>
234	<DT>(5)</DT>
235	<DD>In a string literal, hexadecimal and octal escapes denote the
236	byte with the given value; it is not necessary that the byte
237	encodes a character in the source character set. In a Unicode
238	literal, these escapes denote a Unicode character with the given
239	value.
240	</DD>
241	</DL>
242
243	<P>
244	Unlike Standard <a id='l2h-15' xml:id='l2h-15'></a>C,
245	all unrecognized escape sequences are left in the string unchanged,
246	i.e., <em>the backslash is left in the string</em>. (This behavior is
247	useful when debugging: if an escape sequence is mistyped, the
248	resulting output is more easily recognized as broken.) It is also
249	important to note that the escape sequences marked as ``(Unicode
250	only)'' in the table above fall into the category of unrecognized
251	escapes for non-Unicode string literals.
252
253	<P>
254	When an "<tt class="character">r</tt>" or "<tt class="character">R</tt>" prefix is present, a character
255	following a backslash is included in the string without change, and <em>all
256	backslashes are left in the string</em>. For example, the string literal
257	<code>r"\n"</code> consists of two characters: a backslash and a lowercase
258	"<tt class="character">n</tt>". String quotes can be escaped with a backslash, but the
259	backslash remains in the string; for example, <code>r"\""</code> is a valid string
260	literal consisting of two characters: a backslash and a double quote;
261	<code>r"\"</code> is not a valid string literal (even a raw string cannot
262	end in an odd number of backslashes). Specifically, <em>a raw
263	string cannot end in a single backslash</em> (since the backslash would
264	escape the following quote character). Note also that a single
265	backslash followed by a newline is interpreted as those two characters
266	as part of the string, <em>not</em> as a line continuation.
267
268	<P>
269	When an "<tt class="character">r</tt>" or "<tt class="character">R</tt>" prefix is used in conjunction
270	with a "<tt class="character">u</tt>" or "<tt class="character">U</tt>" prefix, then the <code>\uXXXX</code>
271	escape sequence is processed while <em>all other backslashes are
272	left in the string</em>. For example, the string literal
273	<code>ur"\u0062\n"</code> consists of three Unicode characters: `LATIN
274	SMALL LETTER B', `REVERSE SOLIDUS', and `LATIN SMALL LETTER N'.
275	Backslashes can be escaped with a preceding backslash; however, both
276	remain in the string. As a result, <code>\uXXXX</code> escape sequences
277	are only recognized when there are an odd number of backslashes.
278
279	<P>
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