Mini Shell
"""A thin, practical wrapper around terminal coloring, styling, and
positioning"""
from contextlib import contextmanager
import curses
from curses import setupterm, tigetnum, tigetstr, tparm
from fcntl import ioctl
from six import text_type, string_types
try:
from io import UnsupportedOperation as IOUnsupportedOperation
except ImportError:
class IOUnsupportedOperation(Exception):
"""A dummy exception to take the place of Python 3's
``io.UnsupportedOperation`` in Python 2"""
from os import isatty, environ
import struct
import sys
from termios import TIOCGWINSZ
__all__ = ['Terminal']
class Terminal(object):
"""An abstraction around terminal capabilities
Unlike curses, this doesn't require clearing the screen before doing
anything, and it's friendlier to use. It keeps the endless calls to
``tigetstr()`` and ``tparm()`` out of your code, and it acts intelligently
when somebody pipes your output to a non-terminal.
Instance attributes:
``stream``
The stream the terminal outputs to. It's convenient to pass the stream
around with the terminal; it's almost always needed when the terminal
is and saves sticking lots of extra args on client functions in
practice.
"""
def __init__(self, kind=None, stream=None, force_styling=False):
"""Initialize the terminal.
If ``stream`` is not a tty, I will default to returning an empty
Unicode string for all capability values, so things like piping your
output to a file won't strew escape sequences all over the place. The
``ls`` command sets a precedent for this: it defaults to columnar
output when being sent to a tty and one-item-per-line when not.
:arg kind: A terminal string as taken by ``setupterm()``. Defaults to
the value of the ``TERM`` environment variable.
:arg stream: A file-like object representing the terminal. Defaults to
the original value of stdout, like ``curses.initscr()`` does.
:arg force_styling: Whether to force the emission of capabilities, even
if we don't seem to be in a terminal. This comes in handy if users
are trying to pipe your output through something like ``less -r``,
which supports terminal codes just fine but doesn't appear itself
to be a terminal. Just expose a command-line option, and set
``force_styling`` based on it. Terminal initialization sequences
will be sent to ``stream`` if it has a file descriptor and to
``sys.__stdout__`` otherwise. (``setupterm()`` demands to send them
somewhere, and stdout is probably where the output is ultimately
headed. If not, stderr is probably bound to the same terminal.)
If you want to force styling to not happen, pass
``force_styling=None``.
"""
if stream is None:
stream = sys.__stdout__
try:
stream_descriptor = (stream.fileno() if hasattr(stream, 'fileno')
and callable(stream.fileno)
else None)
except IOUnsupportedOperation:
stream_descriptor = None
self._is_a_tty = (stream_descriptor is not None and
isatty(stream_descriptor))
self._does_styling = ((self.is_a_tty or force_styling) and
force_styling is not None)
# The descriptor to direct terminal initialization sequences to.
# sys.__stdout__ seems to always have a descriptor of 1, even if output
# is redirected.
self._init_descriptor = (sys.__stdout__.fileno()
if stream_descriptor is None
else stream_descriptor)
if self.does_styling:
# Make things like tigetstr() work. Explicit args make setupterm()
# work even when -s is passed to nosetests. Lean toward sending
# init sequences to the stream if it has a file descriptor, and
# send them to stdout as a fallback, since they have to go
# somewhere.
setupterm(kind or environ.get('TERM', 'unknown'),
self._init_descriptor)
self.stream = stream
# Sugary names for commonly-used capabilities, intended to help avoid trips
# to the terminfo man page and comments in your code:
_sugar = dict(
# Don't use "on" or "bright" as an underscore-separated chunk in any of
# these (e.g. on_cology or rock_on) so we don't interfere with
# __getattr__.
save='sc',
restore='rc',
clear_eol='el',
clear_bol='el1',
clear_eos='ed',
# 'clear' clears the whole screen.
position='cup', # deprecated
enter_fullscreen='smcup',
exit_fullscreen='rmcup',
move='cup',
move_x='hpa',
move_y='vpa',
move_left='cub1',
move_right='cuf1',
move_up='cuu1',
move_down='cud1',
hide_cursor='civis',
normal_cursor='cnorm',
reset_colors='op', # oc doesn't work on my OS X terminal.
normal='sgr0',
reverse='rev',
# 'bold' is just 'bold'. Similarly...
# blink
# dim
# flash
italic='sitm',
no_italic='ritm',
shadow='sshm',
no_shadow='rshm',
standout='smso',
no_standout='rmso',
subscript='ssubm',
no_subscript='rsubm',
superscript='ssupm',
no_superscript='rsupm',
underline='smul',
no_underline='rmul')
def __getattr__(self, attr):
"""Return a terminal capability, like bold.
For example, you can say ``term.bold`` to get the string that turns on
bold formatting and ``term.normal`` to get the string that turns it off
again. Or you can take a shortcut: ``term.bold('hi')`` bolds its
argument and sets everything to normal afterward. You can even combine
things: ``term.bold_underline_red_on_bright_green('yowzers!')``.
For a parametrized capability like ``cup``, pass the parameters too:
``some_term.cup(line, column)``.
``man terminfo`` for a complete list of capabilities.
Return values are always Unicode.
"""
resolution = (self._resolve_formatter(attr) if self.does_styling
else NullCallableString())
setattr(self, attr, resolution) # Cache capability codes.
return resolution
@property
def does_styling(self):
"""Whether attempt to emit capabilities
This is influenced by the ``is_a_tty`` property and by the
``force_styling`` argument to the constructor. You can examine
this value to decide whether to draw progress bars or other frippery.
"""
return self._does_styling
@property
def is_a_tty(self):
"""Whether my ``stream`` appears to be associated with a terminal"""
return self._is_a_tty
@property
def height(self):
"""The height of the terminal in characters
If no stream or a stream not representing a terminal was passed in at
construction, return the dimension of the controlling terminal so
piping to things that eventually display on the terminal (like ``less
-R``) work. If a stream representing a terminal was passed in, return
the dimensions of that terminal. If there somehow is no controlling
terminal, return ``None``. (Thus, you should check that the property
``is_a_tty`` is true before doing any math on the result.)
"""
return self._height_and_width()[0]
@property
def width(self):
"""The width of the terminal in characters
See ``height()`` for some corner cases.
"""
return self._height_and_width()[1]
def _height_and_width(self):
"""Return a tuple of (terminal height, terminal width).
Start by trying TIOCGWINSZ (Terminal I/O-Control: Get Window Size),
falling back to environment variables (LINES, COLUMNS), and returning
(None, None) if those are unavailable or invalid.
"""
# tigetnum('lines') and tigetnum('cols') update only if we call
# setupterm() again.
for descriptor in self._init_descriptor, sys.__stdout__:
try:
return struct.unpack(
'hhhh', ioctl(descriptor, TIOCGWINSZ, '\000' * 8))[0:2]
except IOError:
# when the output stream or init descriptor is not a tty, such
# as when when stdout is piped to another program, fe. tee(1),
# these ioctls will raise IOError
pass
try:
return int(environ.get('LINES')), int(environ.get('COLUMNS'))
except TypeError:
return None, None
@contextmanager
def location(self, x=None, y=None):
"""Return a context manager for temporarily moving the cursor.
Move the cursor to a certain position on entry, let you print stuff
there, then return the cursor to its original position::
term = Terminal()
with term.location(2, 5):
print 'Hello, world!'
for x in xrange(10):
print 'I can do it %i times!' % x
Specify ``x`` to move to a certain column, ``y`` to move to a certain
row, both, or neither. If you specify neither, only the saving and
restoration of cursor position will happen. This can be useful if you
simply want to restore your place after doing some manual cursor
movement.
"""
# Save position and move to the requested column, row, or both:
self.stream.write(self.save)
if x is not None and y is not None:
self.stream.write(self.move(y, x))
elif x is not None:
self.stream.write(self.move_x(x))
elif y is not None:
self.stream.write(self.move_y(y))
try:
yield
finally:
# Restore original cursor position:
self.stream.write(self.restore)
@contextmanager
def fullscreen(self):
"""Return a context manager that enters fullscreen mode while inside it
and restores normal mode on leaving."""
self.stream.write(self.enter_fullscreen)
try:
yield
finally:
self.stream.write(self.exit_fullscreen)
@contextmanager
def hidden_cursor(self):
"""Return a context manager that hides the cursor while inside it and
makes it visible on leaving."""
self.stream.write(self.hide_cursor)
try:
yield
finally:
self.stream.write(self.normal_cursor)
@property
def color(self):
"""Return a capability that sets the foreground color.
The capability is unparametrized until called and passed a number
(0-15), at which point it returns another string which represents a
specific color change. This second string can further be called to
color a piece of text and set everything back to normal afterward.
:arg num: The number, 0-15, of the color
"""
return ParametrizingString(self._foreground_color, self.normal)
@property
def on_color(self):
"""Return a capability that sets the background color.
See ``color()``.
"""
return ParametrizingString(self._background_color, self.normal)
@property
def number_of_colors(self):
"""Return the number of colors the terminal supports.
Common values are 0, 8, 16, 88, and 256.
Though the underlying capability returns -1 when there is no color
support, we return 0. This lets you test more Pythonically::
if term.number_of_colors:
...
We also return 0 if the terminal won't tell us how many colors it
supports, which I think is rare.
"""
# This is actually the only remotely useful numeric capability. We
# don't name it after the underlying capability, because we deviate
# slightly from its behavior, and we might someday wish to give direct
# access to it.
if not self._does_styling:
return 0
colors = tigetnum('colors') # Returns -1 if no color support, -2 if no
# such cap.
# self.__dict__['colors'] = ret # Cache it. It's not changing.
# (Doesn't work.)
return colors if colors >= 0 else 0
def _resolve_formatter(self, attr):
"""Resolve a sugary or plain capability name, color, or compound
formatting function name into a callable capability.
Return a ``ParametrizingString`` or a ``FormattingString``.
"""
if attr in COLORS:
return self._resolve_color(attr)
elif attr in COMPOUNDABLES:
# Bold, underline, or something that takes no parameters
return self._formatting_string(self._resolve_capability(attr))
else:
formatters = split_into_formatters(attr)
if all(f in COMPOUNDABLES for f in formatters):
# It's a compound formatter, like "bold_green_on_red". Future
# optimization: combine all formatting into a single escape
# sequence.
return self._formatting_string(
u''.join(self._resolve_formatter(s) for s in formatters))
else:
return ParametrizingString(self._resolve_capability(attr))
def _resolve_capability(self, atom):
"""Return a terminal code for a capname or a sugary name, or an empty
Unicode.
The return value is always Unicode, because otherwise it is clumsy
(especially in Python 3) to concatenate with real (Unicode) strings.
"""
code = tigetstr(self._sugar.get(atom, atom))
if code:
# See the comment in ParametrizingString for why this is latin1.
return code.decode('latin1')
return u''
def _resolve_color(self, color):
"""Resolve a color like red or on_bright_green into a callable
capability."""
# TODO: Does curses automatically exchange red and blue and cyan and
# yellow when a terminal supports setf/setb rather than setaf/setab?
# I'll be blasted if I can find any documentation. The following
# assumes it does.
color_cap = (self._background_color if 'on_' in color else
self._foreground_color)
# curses constants go up to only 7, so add an offset to get at the
# bright colors at 8-15:
offset = 8 if 'bright_' in color else 0
base_color = color.rsplit('_', 1)[-1]
return self._formatting_string(
color_cap(getattr(curses, 'COLOR_' + base_color.upper()) + offset))
@property
def _foreground_color(self):
return self.setaf or self.setf
@property
def _background_color(self):
return self.setab or self.setb
def _formatting_string(self, formatting):
"""Return a new ``FormattingString`` which implicitly receives my
notion of "normal"."""
return FormattingString(formatting, self.normal)
def derivative_colors(colors):
"""Return the names of valid color variants, given the base colors."""
return set([('on_' + c) for c in colors] +
[('bright_' + c) for c in colors] +
[('on_bright_' + c) for c in colors])
COLORS = set(['black', 'red', 'green', 'yellow', 'blue', 'magenta', 'cyan',
'white'])
COLORS.update(derivative_colors(COLORS))
COMPOUNDABLES = (COLORS |
set(['bold', 'underline', 'reverse', 'blink', 'dim', 'italic',
'shadow', 'standout', 'subscript', 'superscript']))
class ParametrizingString(text_type):
"""A Unicode string which can be called to parametrize it as a terminal
capability"""
def __new__(cls, formatting, normal=None):
"""Instantiate.
:arg normal: If non-None, indicates that, once parametrized, this can
be used as a ``FormattingString``. The value is used as the
"normal" capability.
"""
new = text_type.__new__(cls, formatting)
new._normal = normal
return new
def __call__(self, *args):
try:
# Re-encode the cap, because tparm() takes a bytestring in Python
# 3. However, appear to be a plain Unicode string otherwise so
# concats work.
#
# We use *latin1* encoding so that bytes emitted by tparm are
# encoded to their native value: some terminal kinds, such as
# 'avatar' or 'kermit', emit 8-bit bytes in range 0x7f to 0xff.
# latin1 leaves these values unmodified in their conversion to
# unicode byte values. The terminal emulator will "catch" and
# handle these values, even if emitting utf8-encoded text, where
# these bytes would otherwise be illegal utf8 start bytes.
parametrized = tparm(self.encode('latin1'), *args).decode('latin1')
return (parametrized if self._normal is None else
FormattingString(parametrized, self._normal))
except curses.error:
# Catch "must call (at least) setupterm() first" errors, as when
# running simply `nosetests` (without progressive) on nose-
# progressive. Perhaps the terminal has gone away between calling
# tigetstr and calling tparm.
return u''
except TypeError:
# If the first non-int (i.e. incorrect) arg was a string, suggest
# something intelligent:
if len(args) == 1 and isinstance(args[0], string_types):
raise TypeError(
'A native or nonexistent capability template received '
'%r when it was expecting ints. You probably misspelled a '
'formatting call like bright_red_on_white(...).' % args)
else:
# Somebody passed a non-string; I don't feel confident
# guessing what they were trying to do.
raise
class FormattingString(text_type):
"""A Unicode string which can be called upon a piece of text to wrap it in
formatting"""
def __new__(cls, formatting, normal):
new = text_type.__new__(cls, formatting)
new._normal = normal
return new
def __call__(self, text):
"""Return a new string that is ``text`` formatted with my contents.
At the beginning of the string, I prepend the formatting that is my
contents. At the end, I append the "normal" sequence to set everything
back to defaults. The return value is always a Unicode.
"""
return self + text + self._normal
class NullCallableString(text_type):
"""A dummy callable Unicode to stand in for ``FormattingString`` and
``ParametrizingString``
We use this when there is no tty and thus all capabilities should be blank.
"""
def __new__(cls):
new = text_type.__new__(cls, u'')
return new
def __call__(self, *args):
"""Return a Unicode or whatever you passed in as the first arg
(hopefully a string of some kind).
When called with an int as the first arg, return an empty Unicode. An
int is a good hint that I am a ``ParametrizingString``, as there are
only about half a dozen string-returning capabilities on OS X's
terminfo man page which take any param that's not an int, and those are
seldom if ever used on modern terminal emulators. (Most have to do with
programming function keys. Blessings' story for supporting
non-string-returning caps is undeveloped.) And any parametrized
capability in a situation where all capabilities themselves are taken
to be blank are, of course, themselves blank.
When called with a non-int as the first arg (no no args at all), return
the first arg. I am acting as a ``FormattingString``.
"""
if len(args) != 1 or isinstance(args[0], int):
# I am acting as a ParametrizingString.
# tparm can take not only ints but also (at least) strings as its
# second...nth args. But we don't support callably parametrizing
# caps that take non-ints yet, so we can cheap out here. TODO: Go
# through enough of the motions in the capability resolvers to
# determine which of 2 special-purpose classes,
# NullParametrizableString or NullFormattingString, to return, and
# retire this one.
return u''
return args[0] # Should we force even strs in Python 2.x to be
# unicodes? No. How would I know what encoding to use
# to convert it?
def split_into_formatters(compound):
"""Split a possibly compound format string into segments.
>>> split_into_formatters('bold_underline_bright_blue_on_red')
['bold', 'underline', 'bright_blue', 'on_red']
"""
merged_segs = []
# These occur only as prefixes, so they can always be merged:
mergeable_prefixes = ['on', 'bright', 'on_bright']
for s in compound.split('_'):
if merged_segs and merged_segs[-1] in mergeable_prefixes:
merged_segs[-1] += '_' + s
else:
merged_segs.append(s)
return merged_segs
Zerion Mini Shell 1.0