[Python-Dev] CIV

Tim Peters tim_one@email.msn.com
Wed, 4 Oct 2000 00:58:46 -0400

No, that's not 104, it's a Call for Indentation Volunteers!

An item that mistakenly got dropped on the floor before 2.0b1 was to ensure
that the standard Python libraries follow the recommended "4-space indents,
no hard tabs" guideline.  Since 100s of files (especially older ones in
oddball directories) are affected, I moved that it into PEP42 rather than
risk destabilizing the release after 2.0b1.

So it will happen instead soon after 2.0final is released.  I looked at
existing tools for doing this, and found they all left way too much manual
fiddling to bear,  too prone to screw up on comment lines (e.g., try running
your favorite tool over pindent.py:  does the output bear any resemblance to
the input?!  The Emacs pymode does OK there because pindent comments match
its conventions for "indenting comment lines", but nothing else even gets
close; OTOH,

    if 1:    # some insane people like
             # writing comments
             # like this too

and nobody knows what to do about that).

Attached is a new tool that tries much harder to get perverse comments right
(everything else is easy).  Try it and gripe at will.  Since I wrote it
while on vacation, it's public domain <0.5 wink>.

regularly y'rs  - tim

#! /usr/bin/env python

# Released to the public domain, by Tim Peters, 03 October 2000.

"""reindent [-d][-r][-v] path ...

-d  Dry run.  Analyze, but don't make any changes to, files.
-r  Recurse.  Search for all .py files in subdirectories too.
-v  Verbose.  Print informative msgs; else no output.

Change Python (.py) files to use 4-space indents and no hard tab characters.
Also trim excess whitespace from ends of lines, and empty lines at the ends
of files.  Ensure the last line ends with a newline.

Pass one or more file and/or directory paths.  When a directory path, all
.py files within the directory will be examined, and, if the -r option is
given, likewise recursively for subdirectories.

Overwrites files in place, renaming the originals with a .bak extension.
If reindent finds nothing to change, the file is left alone.  If reindent
does change a file, the changed file is a fixed-point for reindent (i.e.,
running reindent on the resulting .py file won't change it again).

The hard part of reindenting is figuring out what to do with comment
lines.  So long as the input files get a clean bill of health from
tabnanny.py, reindent should do a good job.

import tokenize
import os
import sys

verbose = 0
recurse = 0
dryrun  = 0

def errprint(*args):
    sep = ""
    for arg in args:
        sys.stderr.write(sep + str(arg))
        sep = " "

def main():
    import getopt
    global verbose, recurse, dryrun
        opts, args = getopt.getopt(sys.argv[1:], "drv")
    except getopt.error, msg:
    for o, a in opts:
        if o == '-d':
            dryrun += 1
        elif o == '-r':
            recurse += 1
        elif o == '-v':
            verbose += 1
    if not args:
        errprint("Usage:", __doc__)
    for arg in args:

def check(file):
    if os.path.isdir(file) and not os.path.islink(file):
        if verbose:
            print "listing directory", file
        names = os.listdir(file)
        for name in names:
            fullname = os.path.join(file, name)
            if ((recurse and os.path.isdir(fullname) and
                 not os.path.islink(fullname))
                or name.lower().endswith(".py")):

    if verbose:
        print "checking", file, "...",
        f = open(file)
    except IOError, msg:
        errprint("%s: I/O Error: %s" % (file, str(msg)))

    r = Reindenter(f)
    if r.run():
        if verbose:
            print "changed."
            if dryrun:
                print "But this is a dry run, so leaving it alone."
        if not dryrun:
            bak = file + ".bak"
            if os.path.exists(bak):
            os.rename(file, bak)
            if verbose:
                print "renamed", file, "to", bak
            f = open(file, "w")
            if verbose:
                print "wrote new", file
        if verbose:
            print "unchanged."

class Reindenter:

    def __init__(self, f):
        self.find_stmt = 1  # next token begins a fresh stmt?
        self.level = 0      # current indent level

        # Raw file lines.
        self.raw = f.readlines()

        # File lines, rstripped & tab-expanded.  Dummy at start is so
        # that we can use tokenize's 1-based line numbering easily.
        # Note that a line is all-blank iff it's "\n".
        self.lines = [line.rstrip().expandtabs() + "\n"
                      for line in self.raw]
        self.lines.insert(0, None)
        self.index = 1  # index into self.lines of next line

        # List of (lineno, indentlevel) pairs, one for each stmt and
        # comment line.  indentlevel is -1 for comment lines, as a
        # signal that tokenize doesn't know what to do about them;
        # indeed, they're our headache!
        self.stats = []

    def run(self):
        tokenize.tokenize(self.getline, self.tokeneater)
        # Remove trailing empty lines.
        lines = self.lines
        while lines and lines[-1] == "\n":
        # Sentinel.
        stats = self.stats
        stats.append((len(lines), 0))
        # Map count of leading spaces to # we want.
        have2want = {}
        # Program after transformation.
        after = self.after = []
        for i in range(len(stats)-1):
            thisstmt, thislevel = stats[i]
            nextstmt = stats[i+1][0]
            have = getlspace(lines[thisstmt])
            want = thislevel * 4
            if want < 0:
                # A comment line.
                if have:
                    # An indented comment line.  If we saw the same
                    # indentation before, reuse what it most recently
                    # mapped to.
                    want = have2want.get(have, -1)
                    if want < 0:
                        # Then it probably belongs to the next real stmt.
                        for j in xrange(i+1, len(stats)-1):
                            jline, jlevel = stats[j]
                            if jlevel >= 0:
                                if have == getlspace(lines[jline]):
                                    want = jlevel * 4
                    if want < 0:           # Maybe it's a hanging
                                           # comment like this one,
                        # in which case we should shift it like its base
                        # line got shifted.
                        for j in xrange(i-1, -1, -1):
                            jline, jlevel = stats[j]
                            if jlevel >= 0:
                                want = have + getlspace(after[jline-1]) - \
                    if want < 0:
                        # Still no luck -- leave it alone.
                        want = have
                    want = 0
            assert want >= 0
            have2want[have] = want
            diff = want - have
            if diff == 0 or have == 0:
                for line in lines[thisstmt:nextstmt]:
                    if diff > 0:
                        if line == "\n":
                            after.append(" " * diff + line)
                        remove = min(getlspace(line), -diff)
        return self.raw != self.after

    def write(self, f):

    # Line-getter for tokenize.
    def getline(self):
        if self.index >= len(self.lines):
            line = ""
            line = self.lines[self.index]
            self.index += 1
        return line

    # Line-eater for tokenize.
    def tokeneater(self, type, token, (sline, scol), end, line,

        if type == NEWLINE:
            # A program statement, or ENDMARKER, will eventually follow,
            # after some (possibly empty) run of tokens of the form
            #     (NL | COMMENT)* (INDENT | DEDENT+)?
            self.find_stmt = 1

        elif type == INDENT:
            self.find_stmt = 1
            self.level += 1

        elif type == DEDENT:
            self.find_stmt = 1
            self.level -= 1

        elif type == COMMENT:
            if self.find_stmt:
                self.stats.append((sline, -1))
                # but we're still looking for a new stmt, so leave
                # find_stmt alone

        elif type == NL:

        elif self.find_stmt:
            # This is the first "real token" following a NEWLINE, so it
            # must be the first token of the next program statement, or an
            # ENDMARKER.
            self.find_stmt = 0
            if line:   # not endmarker
                self.stats.append((sline, self.level))

# Count number of leading blanks.
def getlspace(line):
    i, n = 0, len(line)
    while i < n and line[i] == " ":
        i += 1
    return i

if __name__ == '__main__':