16.12. curses.ascii — Utilities for ASCII characters

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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 significance in modern usage. The mnemonics derive from teleprinter conventions that predate digital computers.

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

curses.ascii.isalnum(c)

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

curses.ascii.isalpha(c)

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

curses.ascii.isascii(c)

Checks for a character value that fits in the 7-bit ASCII set.

curses.ascii.isblank(c)

Checks for an ASCII whitespace character; space or horizontal tab.

curses.ascii.iscntrl(c)

Checks for an ASCII control character (in the range 0x00 to 0x1f or 0x7f).

curses.ascii.isdigit(c)

Checks for an ASCII decimal digit, '0' through '9'. This is equivalent to c in string.digits.

curses.ascii.isgraph(c)

Checks for ASCII any printable character except space.

curses.ascii.islower(c)

Checks for an ASCII lower-case character.

curses.ascii.isprint(c)

Checks for any ASCII printable character including space.

curses.ascii.ispunct(c)

Checks for any printable ASCII character which is not a space or an alphanumeric character.

curses.ascii.isspace(c)

Checks for ASCII white-space characters; space, line feed, carriage return, form feed, horizontal tab, vertical tab.

curses.ascii.isupper(c)

Checks for an ASCII uppercase letter.

curses.ascii.isxdigit(c)

Checks for an ASCII hexadecimal digit. This is equivalent to c in string.hexdigits.

curses.ascii.isctrl(c)

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

curses.ascii.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.

curses.ascii.ascii(c)

Return the ASCII value corresponding to the low 7 bits of c.

curses.ascii.ctrl(c)

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

curses.ascii.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.

curses.ascii.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.

curses.ascii.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.