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<H1><A NAME="SECTION0081800000000000000000">
6.18 <tt class="module">curses.ascii</tt> --
         Utilities for ASCII characters</A>
</H1>

<P>
<A NAME="module-curses.ascii"></A>

<P>

<span class="versionnote">New in version 1.6.</span>

<P>
The <tt class="module">curses.ascii</tt> module supplies name constants for
ASCII characters and functions to test membership in various
ASCII character classes.  The constants supplied are names for
control characters as follows:

<P>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="left"  >Name</th>
      <th class="left"  >Meaning</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="left"   valign="baseline"><tt class="constant">NUL</tt></td>
        <td class="left"  ></td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">SOH</tt></td>
        <td class="left"  >Start of heading, console interrupt</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">STX</tt></td>
        <td class="left"  >Start of text</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">ETX</tt></td>
        <td class="left"  >End of text</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">EOT</tt></td>
        <td class="left"  >End of transmission</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">ENQ</tt></td>
        <td class="left"  >Enquiry, goes with <tt class="constant">ACK</tt> flow control</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">ACK</tt></td>
        <td class="left"  >Acknowledgement</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">BEL</tt></td>
        <td class="left"  >Bell</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">BS</tt></td>
        <td class="left"  >Backspace</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">TAB</tt></td>
        <td class="left"  >Tab</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">HT</tt></td>
        <td class="left"  >Alias for <tt class="constant">TAB</tt>: ``Horizontal tab''</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">LF</tt></td>
        <td class="left"  >Line feed</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">NL</tt></td>
        <td class="left"  >Alias for <tt class="constant">LF</tt>: ``New line''</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">VT</tt></td>
        <td class="left"  >Vertical tab</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">FF</tt></td>
        <td class="left"  >Form feed</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">CR</tt></td>
        <td class="left"  >Carriage return</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">SO</tt></td>
        <td class="left"  >Shift-out, begin alternate character set</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">SI</tt></td>
        <td class="left"  >Shift-in, resume default character set</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">DLE</tt></td>
        <td class="left"  >Data-link escape</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">DC1</tt></td>
        <td class="left"  >XON, for flow control</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">DC2</tt></td>
        <td class="left"  >Device control 2, block-mode flow control</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">DC3</tt></td>
        <td class="left"  >XOFF, for flow control</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">DC4</tt></td>
        <td class="left"  >Device control 4</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">NAK</tt></td>
        <td class="left"  >Negative acknowledgement</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">SYN</tt></td>
        <td class="left"  >Synchronous idle</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">ETB</tt></td>
        <td class="left"  >End transmission block</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">CAN</tt></td>
        <td class="left"  >Cancel</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">EM</tt></td>
        <td class="left"  >End of medium</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">SUB</tt></td>
        <td class="left"  >Substitute</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">ESC</tt></td>
        <td class="left"  >Escape</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">FS</tt></td>
        <td class="left"  >File separator</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">GS</tt></td>
        <td class="left"  >Group separator</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">RS</tt></td>
        <td class="left"  >Record separator, block-mode terminator</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">US</tt></td>
        <td class="left"  >Unit separator</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">SP</tt></td>
        <td class="left"  >Space</td></tr>
    <tr><td class="left"   valign="baseline"><tt class="constant">DEL</tt></td>
        <td class="left"  >Delete</td></tr></tbody>
</table></div>

<P>
Note that many of these have little practical significance in modern
usage.  The mnemonics derive from teleprinter conventions that predate
digital computers.

<P>
The module supplies the following functions, patterned on those in the
standard C library:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2155' xml:id='l2h-2155' class="function">isalnum</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII alphanumeric character; it is equivalent to
"<tt class="samp">isalpha(<var>c</var>) or isdigit(<var>c</var>)</tt>".
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2156' xml:id='l2h-2156' class="function">isalpha</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII alphabetic character; it is equivalent to
"<tt class="samp">isupper(<var>c</var>) or islower(<var>c</var>)</tt>".
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2157' xml:id='l2h-2157' class="function">isascii</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for a character value that fits in the 7-bit ASCII set.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2158' xml:id='l2h-2158' class="function">isblank</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII whitespace character.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2159' xml:id='l2h-2159' class="function">iscntrl</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII control character (in the range 0x00 to 0x1f).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2160' xml:id='l2h-2160' class="function">isdigit</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII decimal digit, "<tt class="character">0</tt>" through
"<tt class="character">9</tt>".  This is equivalent to "<tt class="samp"><var>c</var> in string.digits</tt>".
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2161' xml:id='l2h-2161' class="function">isgraph</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for ASCII any printable character except space.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2162' xml:id='l2h-2162' class="function">islower</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII lower-case character.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2163' xml:id='l2h-2163' class="function">isprint</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for any ASCII printable character including space.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2164' xml:id='l2h-2164' class="function">ispunct</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for any printable ASCII character which is not a space or an
alphanumeric character.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2165' xml:id='l2h-2165' class="function">isspace</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for ASCII white-space characters; space, line feed,
carriage return, form feed, horizontal tab, vertical tab.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2166' xml:id='l2h-2166' class="function">isupper</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII uppercase letter.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2167' xml:id='l2h-2167' class="function">isxdigit</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII hexadecimal digit.  This is equivalent to
"<tt class="samp"><var>c</var> in string.hexdigits</tt>".
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2168' xml:id='l2h-2168' class="function">isctrl</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for an ASCII control character (ordinal values 0 to 31).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2169' xml:id='l2h-2169' class="function">ismeta</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Checks for a non-ASCII character (ordinal values 0x80 and above).
</dl>

<P>
These functions accept either integers or strings; when the argument
is a string, it is first converted using the built-in function
<tt class="function">ord()</tt>.

<P>
Note that all these functions check ordinal bit values derived from the
first character of the string you pass in; they do not actually know
anything about the host machine's character encoding.  For functions
that know about the character encoding (and handle
internationalization properly) see the <tt class="module"><a href="module-string.html">string</a></tt> module.

<P>
The following two functions take either a single-character string or
integer byte value; they return a value of the same type.

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2170' xml:id='l2h-2170' class="function">ascii</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Return the ASCII value corresponding to the low 7 bits of <var>c</var>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2171' xml:id='l2h-2171' class="function">ctrl</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Return the control character corresponding to the given character
(the character bit value is bitwise-anded with 0x1f).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2172' xml:id='l2h-2172' class="function">alt</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Return the 8-bit character corresponding to the given ASCII character
(the character bit value is bitwise-ored with 0x80).
</dl>

<P>
The following function takes either a single-character string or
integer value; it returns a string.

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2173' xml:id='l2h-2173' class="function">unctrl</tt></b>(</nobr></td>
  <td><var>c</var>)</td></tr></table></dt>
<dd>
Return a string representation of the ASCII character <var>c</var>.  If
<var>c</var> is printable, this string is the character itself.  If the
character is a control character (0x00-0x1f) the string consists of a
caret ("<tt class="character">^</tt>") followed by the corresponding uppercase letter.
If the character is an ASCII delete (0x7f) the string is
<code>'^?'</code>.  If the character has its meta bit (0x80) set, the meta
bit is stripped, the preceding rules applied, and
"<tt class="character">!</tt>" prepended to the result.
</dl>

<P>
<dl><dt><b><tt id='l2h-2174' xml:id='l2h-2174'>controlnames</tt></b></dt>
<dd>
A 33-element string array that contains the ASCII mnemonics for the
thirty-two ASCII control characters from 0 (NUL) to 0x1f (US), in
order, plus the mnemonic "<tt class="samp">SP</tt>" for the space character.
</dd></dl>

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