#!/usr/bin/env python

#

# The MIT License

#

# Copyright (c) 2008 Bob Farrell

#

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

# in the Software without restriction, including without limitation the rights

# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

# copies of the Software, and to permit persons to whom the Software is

# furnished to do so, subject to the following conditions:

#

# The above copyright notice and this permission notice shall be included in

# all copies or substantial portions of the Software.

#

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

# THE SOFTWARE.

#

from __future__ import with_statement

import codecs

import os

import sys

import curses

import code

import traceback

import re

import time

import urllib

import rlcompleter

import inspect

import signal

import struct

import termios

import fcntl

import string

import socket

import pydoc

import types

import unicodedata

from cStringIO import StringIO

from locale import LC_ALL, getpreferredencoding, setlocale

from optparse import OptionParser

from urlparse import urljoin

from xmlrpclib import ServerProxy, Error as XMLRPCError

from ConfigParser import ConfigParser, NoSectionError, NoOptionError

# These are used for syntax hilighting.

from pygments import format

from pygments.lexers import PythonLexer

from pygments.token import Token

from bpython.formatter import BPythonFormatter, Parenthesis

# This for import completion

from bpython import importcompletion

# This for config

from bpython.config import Struct, loadini, migrate_rc

# This for keys

from bpython.keys import key_dispatch

from bpython import __version__

def log(x):

f = open('/tmp/bpython.log', 'a')

f.write('%s\n' % (x,))

orig_stdout = sys.__stdout__

stdscr = None

class FakeStdin(object):

"""Provide a fake stdin type for things like raw_input() etc."""

def __init__(self, interface):

"""Take the curses Repl on init and assume it provides a get_key method

which, fortunately, it does."""

self.encoding = getpreferredencoding()

self.interface = interface

def readline(self):

"""I can't think of any reason why anything other than readline would

be useful in the context of an interactive interpreter so this is the

only one I've done anything with. The others are just there in case

someone does something weird to stop it from blowing up."""

buffer = ''

while True:

key = self.interface.get_key()

sys.stdout.write(key)

# Include the \n in the buffer - raw_input() seems to deal with trailing

# linebreaks and will break if it gets an empty string.

buffer += key

if key == '\n':

break

return buffer

def read(self, x):

pass

def readlines(self, x):

pass

OPTS = Struct()

DO_RESIZE = False

# TODO:

#

# Tab completion does not work if not at the end of the line.

#

# Numerous optimisations can be made but it seems to do all the lookup stuff

# fast enough on even my crappy server so I'm not too bothered about that

# at the moment.

#

# The popup window that displays the argspecs and completion suggestions

# needs to be an instance of a ListWin class or something so I can wrap

# the addstr stuff to a higher level.

#

def DEBUG(s):

"""This shouldn't ever be called in any release of bpython, so

beat me up if you find anything calling it."""

open('/tmp/bpython-debug', 'a').write("%s\n" % (str(s), ))

def get_color(name):

return colors[OPTS.color_scheme[name].lower()]

def get_colpair(name):

return curses.color_pair(get_color(name) + 1)

def make_colors():

"""Init all the colours in curses and bang them into a dictionary"""

# blacK, Red, Green, Yellow, Blue, Magenta, Cyan, White, Default:

c = {

'k' : 0,

'r' : 1,

'g' : 2,

'y' : 3,

'b' : 4,

'm' : 5,

'c' : 6,

'w' : 7,

'd' : -1,

}

for i in range(63):

if i > 7:

j = i / 8

else:

j = c[OPTS.color_scheme['background']]

curses.init_pair(i+1, i % 8, j)

return c

def next_token_inside_string(s, inside_string):

"""Given a code string s and an initial state inside_string, return

whether the next token will be inside a string or not."""

for token, value in PythonLexer().get_tokens(s):

if token is Token.String:

value = value.lstrip('bBrRuU')

if value in ['"""', "'''", '"', "'"]:

if not inside_string:

inside_string = value

elif value == inside_string:

inside_string = False

return inside_string

class Interpreter(code.InteractiveInterpreter):

def __init__(self, encoding):

"""The syntaxerror callback can be set at any time and will be called

on a caught syntax error. The purpose for this in bpython is so that

the repl can be instantiated after the interpreter (which it

necessarily must be with the current factoring) and then an exception

callback can be added to the Interpeter instance afterwards - more

specifically, this is so that autoindentation does not occur after a

traceback."""

self.encoding = encoding

self.syntaxerror_callback = None

# Unfortunately code.InteractiveInterpreter is a classic class, so no super()

code.InteractiveInterpreter.__init__(self)

def runsource(self, source):

source = '# coding: %s\n%s' % (self.encoding,

source.encode(self.encoding))

return code.InteractiveInterpreter.runsource(self, source)

def showsyntaxerror(self, filename=None):

"""Override the regular handler, the code's copied and pasted from

code.py, as per showtraceback, but with the syntaxerror callback called

and the text in a pretty colour."""

if self.syntaxerror_callback is not None:

self.syntaxerror_callback()

type, value, sys.last_traceback = sys.exc_info()

sys.last_type = type

sys.last_value = value

if filename and type is SyntaxError:

# Work hard to stuff the correct filename in the exception

try:

msg, (dummy_filename, lineno, offset, line) = value

except:

# Not the format we expect; leave it alone

pass

else:

# Stuff in the right filename and right lineno

value = SyntaxError(msg, (filename, lineno - 1, offset, line))

sys.last_value = value

list = traceback.format_exception_only(type, value)

self.writetb(list)

def showtraceback(self):

"""This needs to override the default traceback thing

so it can put it into a pretty colour and maybe other

stuff, I don't know"""

try:

t, v, tb = sys.exc_info()

sys.last_type = t

sys.last_value = v

sys.last_traceback = tb

tblist = traceback.extract_tb(tb)

del tblist[:1]

# Set the right lineno (encoding header adds an extra line)

tblist[0] = (tblist[0][0], 1) + tblist[0][2:]

l = traceback.format_list(tblist)

if l:

l.insert(0, "Traceback (most recent call last):\n")

l[len(l):] = traceback.format_exception_only(t, v)

finally:

tblist = tb = None

self.writetb(l)

def writetb(self, l):

"""This outputs the traceback and should be overridden for anything

fancy."""

map(self.write, ["\x01%s\x03%s" % (OPTS.color_scheme['error'], i) for i in l])

class Repl(object):

"""Implements the necessary guff for a Python-repl-alike interface

The execution of the code entered and all that stuff was taken from the

Python code module, I had to copy it instead of inheriting it, I can't

remember why. The rest of the stuff is basically what makes it fancy.

It reads what you type, passes it to a lexer and highlighter which

returns a formatted string. This then gets passed to echo() which

parses that string and prints to the curses screen in appropriate

colours and/or bold attribute.

The Repl class also keeps two stacks of lines that the user has typed in:

One to be used for the undo feature. I am not happy with the way this

works. The only way I have been able to think of is to keep the code

that's been typed in in memory and re-evaluate it in its entirety for each

"undo" operation. Obviously this means some operations could be extremely

slow. I'm not even by any means certain that this truly represents a

genuine "undo" implementation, but it does seem to be generally pretty

effective.

If anyone has any suggestions for how this could be improved, I'd be happy

to hear them and implement it/accept a patch. I researched a bit into the

idea of keeping the entire Python state in memory, but this really seems

very difficult (I believe it may actually be impossible to work) and has

its own problems too.

The other stack is for keeping a history for pressing the up/down keys

to go back and forth between lines.

"""#TODO: Split the class up a bit so the curses stuff isn't so integrated.

"""

"""

def __init__(self, scr, interp, statusbar=None, idle=None):

"""Initialise the repl with, unfortunately, a curses screen passed to

it. This needs to be split up so the curses crap isn't in here.

interp is a Python code.InteractiveInterpreter instance

The optional 'idle' parameter is a function that the repl call while

it's blocking (waiting for keypresses). This, again, should be in a

different class"""

self.cut_buffer = ''

self.buffer = []

self.scr = scr

self.interp = interp

self.match = False

self.rl_hist = []

self.stdout_hist = ''

self.s_hist = []

self.history = []

self.h_i = 0

self.in_hist = False

self.evaluating = False

self.do_exit = False

self.cpos = 0

# Use the interpreter's namespace only for the readline stuff:

self.completer = rlcompleter.Completer(self.interp.locals)

self.completer.attr_matches = self.attr_matches

# Gna, Py 2.6's rlcompleter searches for __call__ inside the

# instance instead of the type, so we monkeypatch to prevent

# side-effects (__getattr__/__getattribute__)

self.completer._callable_postfix = self._callable_postfix

self.statusbar = statusbar

self.list_win = newwin(1, 1, 1, 1)

self.idle = idle

self.f_string = ''

self.matches = []

self.argspec = None

self.s = ''

self.inside_string = False

self.highlighted_paren = None

self.list_win_visible = False

self._C = {}

sys.stdin = FakeStdin(self)

self.paste_mode = False

self.last_key_press = time.time()

self.paste_time = 0.02

sys.path.insert(0, '.')

if not OPTS.arg_spec:

return

pythonhist = os.path.expanduser('~/.pythonhist')

if os.path.exists(pythonhist):

with codecs.open(pythonhist, 'r', getpreferredencoding(),

'ignore') as hfile:

self.rl_hist = hfile.readlines()

def clean_object(self, obj):

"""Try to make an object not exhibit side-effects on attribute

lookup. Return the type's magic attributes so they can be reapplied

with restore_object"""

type_ = type(obj)

__getattribute__ = None

__getattr__ = None

# Dark magic:

# If __getattribute__ doesn't exist on the class and __getattr__ does

# then __getattr__ will be called when doing

# getattr(type_, '__getattribute__', None)

# so we need to first remove the __getattr__, then the

# __getattribute__, then look up the attributes and then restore the

# original methods. :-(

# The upshot being that introspecting on an object to display its

# attributes will avoid unwanted side-effects.

if type_ != types.InstanceType:

__getattr__ = getattr(type_, '__getattr__', None)

if __getattr__ is not None:

try:

setattr(type_, '__getattr__', (lambda _: None))

except TypeError:

__getattr__ = None

__getattribute__ = getattr(type_, '__getattribute__', None)

if __getattribute__ is not None:

try:

setattr(type_, '__getattribute__', object.__getattribute__)

except TypeError:

# XXX: This happens for e.g. built-in types

__getattribute__ = None

# /Dark magic

return __getattribute__, __getattr__

def restore_object(self, obj, attribs):

"""Restore an object's magic methods as returned from clean_object"""

type_ = type(obj)

__getattribute__, __getattr__ = attribs

# Dark magic:

if __getattribute__ is not None:

setattr(type_, '__getattribute__', __getattribute__)

if __getattr__ is not None:

setattr(type_, '__getattr__', __getattr__)

# /Dark magic

def attr_matches(self, text):

"""Taken from rlcompleter.py and bent to my will."""

m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)

if not m:

return []

expr, attr = m.group(1, 3)

obj = eval(expr, self.interp.locals)

attribs = self.clean_object(obj)

try:

matches = self.attr_lookup(obj, expr, attr)

finally:

self.restore_object(obj, attribs)

return matches

def attr_lookup(self, obj, expr, attr):

"""Second half of original attr_matches method factored out so it can

be wrapped in a safe try/finally block in case anything bad happens to

restore the original __getattribute__ method."""

words = dir(obj)

if hasattr(obj, '__class__'):

words.append('__class__')

words = words + rlcompleter.get_class_members(obj.__class__)

matches = []

n = len(attr)

for word in words:

if word[:n] == attr and word != "__builtins__":

matches.append("%s.%s" % (expr, word))

return matches

def _callable_postfix(self, value, word):

"""rlcompleter's _callable_postfix done right."""

attribs = self.clean_object(value)

try:

if hasattr(value, '__call__'):

word += '('

finally:

self.restore_object(value, attribs)

return word

def cw(self):

"""Return the current word, i.e. the (incomplete) word directly to the

left of the cursor"""

if self.cpos:

# I don't know if autocomplete should be disabled if the cursor

# isn't at the end of the line, but that's what this does for now.

return

l = len(self.s)

if (not self.s or

(not self.s[l-1].isalnum() and

self.s[l-1] not in ('.', '_'))):

return

i = 1

while i < l+1:

if not self.s[-i].isalnum() and self.s[-i] not in ('.', '_'):

break

i += 1

return self.s[-i +1:]

def get_args(self):

"""Check if an unclosed parenthesis exists, then attempt to get the

argspec() for it. On success, update self.argspec and return True,

otherwise set self.argspec to None and return False"""

def getpydocspec(f, func):

try:

argspec = pydoc.getdoc(f)

except NameError:

return None

rx = re.compile(r'([a-zA-Z_][a-zA-Z0-9_]*?)\((.*?)\)')

s = rx.search(argspec)

if s is None:

return None

if s.groups()[0] != func:

return None

args = [i.strip() for i in s.groups()[1].split(',')]

return [func, (args, None, None, None)]

def getargspec(func):

try:

if func in self.interp.locals:

f = self.interp.locals[func]

except TypeError:

return None

else:

try:

f = eval(func, self.interp.locals)

except Exception:

# Same deal with the exceptions :(

return None

is_bound_method = inspect.ismethod(f) and f.im_self is not None

try:

if inspect.isclass(f):

argspec = inspect.getargspec(f.__init__)

is_bound_method = True

else:

argspec = inspect.getargspec(f)

self.argspec = [func, argspec, is_bound_method]

return True

except (NameError, TypeError, KeyError):

t = getpydocspec(f, func)

if t is None:

return None

self.argspec = t

self.argspec.append(is_bound_method)

return True

except AttributeError:

# This happens if no __init__ is found

return None

if not OPTS.arg_spec:

return False

stack = [['', 0, '']]

try:

for (token, value) in PythonLexer().get_tokens(self.s):

if token is Token.Punctuation:

if value in '([{':

stack.append(['', 0, value])

elif value in ')]}':

stack.pop()

elif value == ',':

try:

stack[-1][1] += 1

except TypeError:

stack[-1][1] = ''

elif (token is Token.Name or token in Token.Name.subtypes or

token is Token.Operator and value == '.'):

stack[-1][0] += value

elif token is Token.Operator and value == '=':

stack[-1][1] = stack[-1][0]

else:

stack[-1][0] = ''

while stack[-1][2] in '[{':

stack.pop()

_, arg_number, _ = stack.pop()

func, _, _ = stack.pop()

except IndexError:

return False

if getargspec(func):

self.argspec.append(arg_number)

return True

return False

def check(self):

"""Check if paste mode should still be active and, if not, deactivate

it and force syntax highlighting."""

if (self.paste_mode

and time.time() - self.last_key_press > self.paste_time):

self.paste_mode = False

self.print_line(self.s)

def complete(self, tab=False):

"""Wrap the _complete method to determine the visibility of list_win

since there can be several reasons why it won't be displayed; this

makes it more manageable."""

if self.paste_mode and self.list_win_visible:

self.scr.touchwin()

if self.paste_mode:

return

if self.list_win_visible and not OPTS.auto_display_list:

self.scr.touchwin()

self.list_win_visible = False

return

if OPTS.auto_display_list or tab:

self.list_win_visible = self._complete(tab)

return

def _complete(self, unused_tab=False):

"""Construct a full list of possible completions and construct and

display them in a window. Also check if there's an available argspec

(via the inspect module) and bang that on top of the completions too.

The return value is whether the list_win is visible or not."""

if not self.get_args():

self.argspec = None

cw = self.cw()

if not (cw or self.argspec):

self.scr.redrawwin()

self.scr.refresh()

return False

if not cw:

self.matches = []

# Check for import completion

e = False

matches = importcompletion.complete(self.s, cw)

if matches is None:

self.scr.redrawwin()

return False

if not matches:

# Nope, no import, continue with normal completion

try:

self.completer.complete(cw, 0)

except Exception:

# This sucks, but it's either that or list all the exceptions that could

# possibly be raised here, so if anyone wants to do that, feel free to send me

# a patch. XXX: Make sure you raise here if you're debugging the completion

# stuff !

e = True

else:

matches = self.completer.matches

if e or not matches:

self.matches = []

if not self.argspec:

self.scr.redrawwin()

return False

if not e and matches:

# remove duplicates and restore order

self.matches = sorted(set(matches))

if len(self.matches) == 1 and not OPTS.auto_display_list:

self.list_win_visible = True

self.tab()

return False

self.show_list(self.matches, self.argspec)

return True

def show_list(self, items, topline=None):

shared = Struct()

shared.cols = 0

shared.rows = 0

shared.wl = 0

y, x = self.scr.getyx()

h, w = self.scr.getmaxyx()

down = (y < h / 2)

if down:

max_h = h - y

else:

max_h = y+1

max_w = int(w * 0.8)

self.list_win.erase()

if items and '.' in items[0]:

items = [x.rsplit('.')[-1] for x in items]

if topline:

height_offset = self.mkargspec(topline, down) + 1

else:

height_offset = 0

def lsize():

wl = max(len(i) for i in v_items) + 1

if not wl:

wl = 1

cols = ((max_w - 2) / wl) or 1

rows = len(v_items) / cols

if cols * rows < len(v_items):

rows += 1

if rows + 2 >= max_h:

rows = max_h - 2

return False

shared.rows = rows

shared.cols = cols

shared.wl = wl

return True

if items:

# visible items (we'll append until we can't fit any more in)

v_items = [items[0][:max_w-3]]

lsize()

else:

v_items = []

for i in items[1:]:

v_items.append(i[:max_w-3])

if not lsize():

del v_items[-1]

v_items[-1] = '...'

break

rows = shared.rows

if rows + height_offset < max_h:

rows += height_offset

display_rows = rows

else:

display_rows = rows + height_offset

cols = shared.cols

wl = shared.wl

if topline and not v_items:

w = max_w

elif wl + 3 > max_w:

w = max_w

else:

t = (cols + 1) * wl + 3

if t > max_w:

t = max_w

w = t

if height_offset and display_rows+5 >= max_h:

del v_items[-(cols * (height_offset)):]

self.list_win.resize(rows+2, w)

if down:

self.list_win.mvwin(y+1, 0)

else:

self.list_win.mvwin(y-rows-2, 0)

if v_items:

self.list_win.addstr('\n ')

for ix, i in enumerate(v_items):

padding = (wl - len(i)) * ' '

self.list_win.addstr(i + padding, get_colpair('main'))

if ((cols == 1 or (ix and not (ix+1) % cols))

and ix + 1 < len(v_items)):

self.list_win.addstr('\n ')

# XXX: After all the trouble I had with sizing the list box (I'm not very good

# at that type of thing) I decided to do this bit of tidying up here just to

# make sure there's no unnececessary blank lines, it makes things look nicer.

y = self.list_win.getyx()[0]

self.list_win.resize(y + 2, w)

self.statusbar.win.touchwin()

self.statusbar.win.noutrefresh()

self.list_win.attron(get_colpair('main'))

self.list_win.border()

self.scr.touchwin()

self.scr.cursyncup()

self.scr.noutrefresh()

# This looks a little odd, but I can't figure a better way to stick the cursor

# back where it belongs (refreshing the window hides the list_win)

self.scr.move(*self.scr.getyx())

self.list_win.refresh()

def mkargspec(self, topline, down):

"""This figures out what to do with the argspec and puts it nicely into

the list window. It returns the number of lines used to display the

argspec. It's also kind of messy due to it having to call so many

addstr() to get the colouring right, but it seems to be pretty

sturdy."""

r = 3

fn = topline[0]

args = topline[1][0]

kwargs = topline[1][3]

_args = topline[1][1]

_kwargs = topline[1][2]

is_bound_method = topline[2]

in_arg = topline[3]

max_w = int(self.scr.getmaxyx()[1] * 0.6)

self.list_win.erase()

self.list_win.resize(3, max_w)

h, w = self.list_win.getmaxyx()

self.list_win.addstr('\n ')

self.list_win.addstr(fn,

get_colpair('name') | curses.A_BOLD)

self.list_win.addstr(': (', get_colpair('name'))

maxh = self.scr.getmaxyx()[0]

if is_bound_method and isinstance(in_arg, int):

in_arg += 1

for k, i in enumerate(args):

y, x = self.list_win.getyx()

ln = len(str(i))

kw = None

if kwargs and k+1 > len(args) - len(kwargs):

kw = str(kwargs[k - (len(args) - len(kwargs))])

ln += len(kw) + 1

if ln + x >= w:

ty = self.list_win.getbegyx()[0]

if not down and ty > 0:

h +=1

self.list_win.mvwin(ty-1, 1)

self.list_win.resize(h, w)

elif down and h + r < maxh-ty:

h += 1

self.list_win.resize(h, w)

else:

break

r += 1

self.list_win.addstr('\n\t')

if str(i) == 'self' and k == 0:

color = get_colpair('name')

else:

color = get_colpair('token')

if k == in_arg or i == in_arg:

color |= curses.A_BOLD

self.list_win.addstr(str(i), color)

if kw:

self.list_win.addstr('=', get_colpair('punctuation'))

self.list_win.addstr(kw, get_colpair('token'))

if k != len(args) -1:

self.list_win.addstr(', ', get_colpair("punctuation"))

if _args:

if args:

self.list_win.addstr(', ', get_colpair('punctuation'))

self.list_win.addstr('*%s' % (_args, ), get_colpair('token'))

if _kwargs:

if args or _args:

self.list_win.addstr(', ', get_colpair('punctuation'))

self.list_win.addstr('**%s' % (_kwargs, ), get_colpair('token'))

self.list_win.addstr(')', get_colpair('punctuation'))

return r

def getstdout(self):

"""This method returns the 'spoofed' stdout buffer, for writing to a

file or sending to a pastebin or whatever."""

return self.stdout_hist + '\n'

def formatforfile(self, s):

"""Format the stdout buffer to something suitable for writing to disk,

i.e. without >>> and ... at input lines and with "# OUT: " prepended to

output lines."""

def process():

for line in s.split('\n'):

if line.startswith('>>>') or line.startswith('...'):

yield line[4:]

elif line.rstrip():

yield "# OUT: %s" % (line,)

return "\n".join(process())

def write2file(self):

"""Prompt for a filename and write the current contents of the stdout

buffer to disk."""

try:

fn = self.statusbar.prompt('Save to file (Esc to cancel): ')

except ValueError:

self.statusbar.message("Save cancelled.")

return

if fn.startswith('~'):

fn = os.path.expanduser(fn)

s = self.formatforfile(self.getstdout())

try:

f = open(fn, 'w')

f.write(s)

f.close()

except IOError:

self.statusbar.message("Disk write error for file '%s'." % (fn, ))

else:

self.statusbar.message('Saved to %s' % (fn, ))

def pastebin(self):

"""Upload to a pastebin and display the URL in the status bar."""

pasteservice_url = 'http://paste.pocoo.org/'

pasteservice = ServerProxy(urljoin(pasteservice_url, '/xmlrpc/'))

s = self.getstdout()

self.statusbar.message('Posting data to pastebin...')

try:

paste_id = pasteservice.pastes.newPaste('pycon', s)

except XMLRPCError, e:

self.statusbar.message( 'Upload failed: %s' % (str(e), ) )

return

paste_url = urljoin(pasteservice_url, '/show/%s/' % (paste_id, ))

self.statusbar.message('Pastebin URL: %s' % (paste_url, ), 10)

def make_list(self, items):

"""Compile a list of items. At the moment this simply returns

the list; it's here in case I decide to add any more functionality.

I originally had this method return a list of items where each item

was prepended with a number/letter so the user could choose an option

but it doesn't seem appropriate for readline-like behaviour."""

return items

def push(self, s):

"""Push a line of code onto the buffer so it can process it all

at once when a code block ends"""

s = s.rstrip('\n')

self.buffer.append(s)

try:

more = self.interp.runsource('\n'.join(self.buffer))

except SystemExit:

# Avoid a traceback on e.g. quit()

self.do_exit = True

return False

if not more:

self.buffer = []

return more

def undo(self, n=1):

"""Go back in the undo history n steps and call reeavluate()

Note that in the program this is called "Rewind" because I

want it to be clear that this is by no means a true undo

implementation, it is merely a convenience bonus."""

if not self.history:

return None

if len(self.history) < n:

n = len(self.history)

self.history = self.history[:-n]

self.reevaluate()

def enter_hist(self):

"""Set flags for entering into the history by pressing up/down"""

if not self.in_hist:

self.in_hist = True

self.ts = self.s

def back(self):

"""Replace the active line with previous line in history and

increment the index to keep track"""

if not self.rl_hist:

return None

self.cpos = 0

self.enter_hist()

if self.h_i < len(self.rl_hist):

self.h_i += 1

self.s = self.rl_hist[-self.h_i].rstrip('\n')

self.print_line(self.s, clr=True)

def fwd(self):

"""Same as back() but, well, forward"""

self.enter_hist()

self.cpos = 0

if self.h_i > 1:

self.h_i -= 1

self.s = self.rl_hist[-self.h_i].rstrip('\n')

else:

self.h_i = 0

self.s = self.ts

self.ts = ''

self.in_hist = False

self.print_line(self.s, clr=True)

def redraw(self):

"""Redraw the screen."""

self.scr.erase()

for k, s in enumerate(self.s_hist):

if not s:

continue

self.iy, self.ix = self.scr.getyx()

for i in s.split('\x04'):

self.echo(i, redraw=False)

if k < len(self.s_hist) -1:

self.scr.addstr('\n')

self.iy, self.ix = self.scr.getyx()

self.print_line(self.s)

self.scr.refresh()

self.statusbar.refresh()

def reevaluate(self):

"""Clear the buffer, redraw the screen and re-evaluate the history"""

self.evaluating = True

self.stdout_hist = ''

self.f_string = ''

self.buffer = []

self.scr.erase()

self.s_hist = []

self.prompt(False)

self.iy, self.ix = self.scr.getyx()