6.15 curses.ascii -- Utilities for ASCII characters
Keywords: lib

# 6.15 `curses.ascii` -- Utilities for ASCII characters

New in version 1.6.

The `curses.ascii` 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:

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

Note that many of these have little practical use in modern usage.

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

`isalnum` (c)
  Checks for an ASCII alphanumeric character; it is equivalent to "`isalpha(c) or isdigit(c)`".

`isalpha` (c)
  Checks for an ASCII alphabetic character; it is equivalent to "`isupper(c) or islower(c)`".

`isascii` (c)
  Checks for a character value that fits in the 7-bit ASCII set.

`isblank` (c)
  Checks for an ASCII whitespace character.

`iscntrl` (c)
  Checks for an ASCII control character (in the range 0x00 to 0x1f).

`isdigit` (c)
  Checks for an ASCII decimal digit, "`0`" through "`9`". This is equivalent to "`c in string.digits`".

`isgraph` (c)
  Checks for ASCII any printable character except space.

`islower` (c)
  Checks for an ASCII lower-case character.

`isprint` (c)
  Checks for any ASCII printable character including space.

`ispunct` (c)
  Checks for any printable ASCII character which is not a space or an alphanumeric character.

`isspace` (c)
  Checks for ASCII white-space characters; space, tab, line feed, carriage return, form feed, horizontal tab, vertical tab.

`isupper` (c)
  Checks for an ASCII uppercase letter.

`isxdigit` (c)
  Checks for an ASCII hexadecimal digit. This is equivalent to "`c in string.hexdigits`".

`isctrl` (c)
  Checks for an ASCII control character (ordinal values 0 to 31).

`ismeta` (c)
  Checks for a non-ASCII character (ordinal values 0x80 and above).

These functions accept either integers or strings; when the argument is a string, it is first converted using the built-in function `ord()`.

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 `string` module.

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

`ascii` (c)
  Return the ASCII value corresponding to the low 7 bits of c.

`ctrl` (c)
  Return the control character corresponding to the given character (the character bit value is bitwise-anded with 0x1f).

`alt` (c)
  Return the 8-bit character corresponding to the given ASCII character (the character bit value is bitwise-ored with 0x80).

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

`unctrl` (c)
  Return a string representation of the ASCII character c. If c is printable, this string is the character itself. If the character is a control character (0x00-0x1f) the string consists of a caret ("`^`") followed by the corresponding uppercase letter. If the character is an ASCII delete (0x7f) the string is `'^?'`. If the character has its meta bit (0x80) set, the meta bit is stripped, the preceding rules applied, and "`!`" prepended to the result.

`controlnames`
  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 "`SP`" for the space character.