Well, now you ask for it... How about the attached program,
tentatively called "pindent"? Pindent -c "completes" a program, i.e.
adds block terminators assuming its input is validly indented; pindent
-r "reformats" a program, i.e. generates proper indentation assuming
the input has block terminators.
> If the Python compiler would allow for an optional filter, you're all
> set. This can even work with code within a string literal, given that
> the formatter is smart enough to recognize it and know how to add
> newlines to a string literal.
I don't think it's necessary to build this into the Python
interpreter. From the discussion so far I gather that when there's
danger of ill-formatted code, there's always some program that takes
the code from the user and hands it over to the interpreter. This
could could call pindent as a filter.
--Guido van Rossum, CWI, Amsterdam <Guido.van.Rossum@cwi.nl>
URL: <http://www.cwi.nl/cwi/people/Guido.van.Rossum.html>
#! /usr/local/bin/python
# This file contains a class and a main program that perform two
# related (though complimentary) formatting operations on Python
# programs. When called as "pindend -c", it takes a valid Python
# program as input and outputs a version augmented with block-closing
# comments. When called as "pindent -r" it assumes its input is a
# Python program with block-closing comments but with its indentation
# messed up, and outputs a properly indented version.
# A "block-closing comment" is a comment of the form '# end <keyword>'
# where <keyword> is the keyword that opened the block. If the
# opening keyword is 'def' or 'class', the function or class name may
# be repeated in the block-closing comment as well. Here is an
# example of a program fully augmented with block-closing comments:
# def foobar(a, b):
# if a == b:
# a = a+1
# elif a < b:
# b = b-1
# if b > a: a = a-1
# # end if
# else:
# print 'oops!'
# # end if
# # end def foobar
# Note that only the last part of an if...elif...else... block needs a
# block-closing comment; the same is true for other compound
# statements (e.g. try...except). Also note that "short-form" blocks
# like the second 'if' in the example must be closed as well;
# otherwise the 'else' in the example would be ambiguous (remember
# that indentation is not significant when interpreting block-closing
# comments).
# Both operations are idempotent (i.e. applied to their own output
# they yield an identical result). Running first "pindent -c" and
# then "pindent -r" on a valid Python program produces a program that
# is semantically identical to the input (though its indentation may
# be different).
# Other options:
# -s stepsize: set the indentation step size (default 8)
# -t tabsize : set the number of spaces a tab character is worth (default 8)
# file ... : input file(s) (default standard input)
# The results always go to standard output
# Caveats:
# - comments ending in a backslash will be mistaken for continued lines
# - continuations using backslash are always left unchanged
# - continuations inside parentheses are not extra indented by -r
# but must be indented for -c to work correctly (this breaks
# idempotency!)
# - continued lines inside triple-quoted strings are totally garbled
# Secret feature:
# - On input, a block may also be closed with an "end statement" --
# this is a block-closing comment without the '#' sign.
# Possible improvements:
# - check syntax based on transitions in 'next' table
# - better error reporting
# - better error recovery
# - check identifier after class/def
# The following wishes need a more complete tokenization of the source:
# - Don't get fooled by comments ending in backslash
# - reindent continuation lines indicated by backslash
# - handle continuation lines inside parentheses/braces/brackets
# - handle triple quoted strings spanning lines
# - realign comments
# - optionally do much more thorough reformatting, a la C indent
import os
import regex
import string
import sys
next = {}
next['if'] = next['elif'] = 'elif', 'else', 'end'
next['while'] = next['for'] = 'else', 'end'
next['try'] = 'except', 'finally'
next['except'] = 'except', 'else', 'end'
next['else'] = next['finally'] = next['def'] = next['class'] = 'end'
next['end'] = ()
start = 'if', 'while', 'for', 'try', 'def', 'class'
class PythonIndenter:
def __init__(self, fpi = sys.stdin, fpo = sys.stdout,
indentsize = 8, tabsize = 8):
self.fpi = fpi
self.fpo = fpo
self.indentsize = indentsize
self.tabsize = tabsize
self.lineno = 0
self.write = fpo.write
self.kwprog = regex.symcomp(
'^[ \t]*\(<kw>[a-z]+\)'
'\([ \t]+\(<id>[a-zA-Z_][a-zA-Z0-9_]*\)\)?'
'[^a-zA-Z0-9_]')
self.endprog = regex.symcomp(
'^[ \t]*#?[ \t]*end[ \t]+\(<kw>[a-z]+\)'
'\([ \t]+\(<id>[a-zA-Z_][a-zA-Z0-9_]*\)\)?'
'[^a-zA-Z0-9_]')
self.wsprog = regex.compile('^[ \t]*')
# end def __init__
def readline(self):
line = self.fpi.readline()
if line: self.lineno = self.lineno + 1
# end if
return line
# end def readline
def error(self, fmt, *args):
if args: fmt = fmt % args
# end if
sys.stderr.write('Error at line %d: %s\n' % (self.lineno, fmt))
self.write('### %s ###\n' % fmt)
# end def error
def getline(self):
line = self.readline()
while line[-2:] == '\\\n':
line2 = self.readline()
if not line2: break
# end if
line = line + line2
# end while
return line
# end def getline
def putline(self, line, indent = None):
if indent is None:
self.write(line)
return
# end if
tabs, spaces = divmod(indent*self.indentsize, self.tabsize)
i = max(0, self.wsprog.match(line))
self.write('\t'*tabs + ' '*spaces + line[i:])
# end def putline
def reformat(self):
stack = []
while 1:
line = self.getline()
if not line: break # EOF
# end if
if self.endprog.match(line) >= 0:
kw = 'end'
kw2 = self.endprog.group('kw')
if not stack:
self.error('unexpected end')
elif stack[-1][0] != kw2:
self.error('unmatched end')
# end if
del stack[-1:]
self.putline(line, len(stack))
continue
# end if
if self.kwprog.match(line) >= 0:
kw = self.kwprog.group('kw')
if kw in start:
self.putline(line, len(stack))
stack.append((kw, kw))
continue
# end if
if next.has_key(kw) and stack:
self.putline(line, len(stack)-1)
kwa, kwb = stack[-1]
stack[-1] = kwa, kw
continue
# end if
# end if
self.putline(line, len(stack))
# end while
if stack:
self.error('unterminated keywords')
for kwa, kwb in stack:
self.write('\t%s\n' % kwa)
# end for
# end if
# end def reformat
def complete(self):
self.indentsize = 1
stack = []
todo = []
current, firstkw, lastkw, topid = 0, '', '', ''
while 1:
line = self.getline()
i = max(0, self.wsprog.match(line))
if self.endprog.match(line) >= 0:
thiskw = 'end'
endkw = self.endprog.group('kw')
thisid = self.endprog.group('id')
elif self.kwprog.match(line) >= 0:
thiskw = self.kwprog.group('kw')
if not next.has_key(thiskw):
thiskw = ''
# end if
if thiskw in ('def', 'class'):
thisid = self.kwprog.group('id')
else:
thisid = ''
# end if
elif line[i:i+1] in ('\n', '#'):
todo.append(line)
continue
else:
thiskw = ''
# end if
indent = len(string.expandtabs(line[:i], self.tabsize))
while indent < current:
if firstkw:
if topid:
s = '# end %s %s\n' % (
firstkw, topid)
else:
s = '# end %s\n' % firstkw
# end if
self.putline(s, current)
firstkw = lastkw = ''
# end if
current, firstkw, lastkw, topid = stack[-1]
del stack[-1]
# end while
if indent == current and firstkw:
if thiskw == 'end':
if endkw != firstkw:
self.error('mismatched end')
# end if
firstkw = lastkw = ''
elif not thiskw or thiskw in start:
if topid:
s = '# end %s %s\n' % (
firstkw, topid)
else:
s = '# end %s\n' % firstkw
# end if
self.putline(s, current)
firstkw = lastkw = topid = ''
# end if
# end if
if indent > current:
stack.append(current, firstkw, lastkw, topid)
if thiskw and thiskw not in start:
# error
thiskw = ''
# end if
current, firstkw, lastkw, topid = \
indent, thiskw, thiskw, thisid
# end if
if thiskw:
if thiskw in start:
firstkw = lastkw = thiskw
topid = thisid
else:
lastkw = thiskw
# end if
# end if
for l in todo: self.write(l)
# end for
todo = []
if not line: break
# end if
self.write(line)
# end while
# end def complete
# end class PythonIndenter
def test():
import getopt
opts, args = getopt.getopt(sys.argv[1:], 'crs:t:')
action = None
stepsize = 8
tabsize = 8
for o, a in opts:
if o == '-c':
action = PythonIndenter.complete
elif o == '-r':
action = PythonIndenter.reformat
elif p == '-s':
stepsize = string.atoi(a)
elif p == '-t':
tabsize = string.atoi(a)
# end if
# end for
if not action:
print 'You must specify -c(omplete) or -r(eformat)'
sys.exit(2)
# end if
if not args: args = ['-']
# end if
for file in args:
if file == '-':
fp = sys.stdin
else:
fp = open(file, 'r')
# end if
pi = PythonIndenter(fp, sys.stdout, stepsize, tabsize)
action(pi)
if fp != sys.stdin: fp.close()
# end if
# end for
# end def test
if __name__ == '__main__':
test()
# end if