#! /usr/bin/env python # Fix Python source files to use the new equality test operator, i.e.,#       if x = y: ...# is changed to#       if x == y: ...# The script correctly tokenizes the Python program to reliably# distinguish between assignments and equality tests.## Command line arguments are files or directories to be processed.# Directories are searched recursively for files whose name looks# like a python module.# Symbolic links are always ignored (except as explicit directory# arguments).  Of course, the original file is kept as a back-up# (with a "~" attached to its name).# It complains about binaries (files containing null bytes)# and about files that are ostensibly not Python files: if the first# line starts with '#!' and does not contain the string 'python'.## Changes made are reported to stdout in a diff-like format.## Undoubtedly you can do this using find and sed or perl, but this is# a nice example of Python code that recurses down a directory tree# and uses regular expressions.  Also note several subtleties like# preserving the file's mode and avoiding to even write a temp file# when no changes are needed for a file.## NB: by changing only the function fixline() you can turn this# into a program for a different change to Python programs... import sysimport reimport osfrom stat import *import string err = sys.stderr.writedbg = errrep = sys.stdout.write def main():    bad = 0    if not sys.argv[1:]: # No arguments        err('usage: ' + sys.argv[0] + ' file-or-directory ...\n')        sys.exit(2)    for arg in sys.argv[1:]:        if os.path.isdir(arg):            if recursedown(arg): bad = 1        elif os.path.islink(arg):            err(arg + ': will not process symbolic links\n')            bad = 1        else:            if fix(arg): bad = 1    sys.exit(bad) ispythonprog = re.compile('^[a-zA-Z0-9_]+\.py$')def ispython(name):    return ispythonprog.match(name) >= 0 def recursedown(dirname):    dbg('recursedown(%r)\n' % (dirname,))    bad = 0    try:        names = os.listdir(dirname)    except os.error, msg:        err('%s: cannot list directory: %r\n' % (dirname, msg))        return 1    names.sort()    subdirs = []    for name in names:        if name in (os.curdir, os.pardir): continue        fullname = os.path.join(dirname, name)        if os.path.islink(fullname): pass        elif os.path.isdir(fullname):            subdirs.append(fullname)        elif ispython(name):            if fix(fullname): bad = 1    for fullname in subdirs:        if recursedown(fullname): bad = 1    return bad def fix(filename):##      dbg('fix(%r)\n' % (dirname,))    try:        f = open(filename, 'r')    except IOError, msg:        err('%s: cannot open: %r\n' % (filename, msg))        return 1    head, tail = os.path.split(filename)    tempname = os.path.join(head, '@' + tail)    g = None    # If we find a match, we rewind the file and start over but    # now copy everything to a temp file.    lineno = 0    while 1:        line = f.readline()        if not line: break        lineno = lineno + 1        if g is None and '\0' in line:            # Check for binary files            err(filename + ': contains null bytes; not fixed\n')            f.close()            return 1        if lineno == 1 and g is None and line[:2] == '#!':            # Check for non-Python scripts            words = string.split(line[2:])            if words and re.search('[pP]ython', words[0]) < 0:                msg = filename + ': ' + words[0]                msg = msg + ' script; not fixed\n'                err(msg)                f.close()                return 1        while line[-2:] == '\\\n':            nextline = f.readline()            if not nextline: break            line = line + nextline            lineno = lineno + 1        newline = fixline(line)        if newline != line:            if g is None:                try:                    g = open(tempname, 'w')                except IOError, msg:                    f.close()                    err('%s: cannot create: %r\n' % (tempname, msg))                    return 1                f.seek(0)                lineno = 0                rep(filename + ':\n')                continue # restart from the beginning            rep(repr(lineno) + '\n')            rep('< ' + line)            rep('> ' + newline)        if g is not None:            g.write(newline)     # End of file    f.close()    if not g: return 0 # No changes     # Finishing touch -- move files     # First copy the file's mode to the temp file    try:        statbuf = os.stat(filename)        os.chmod(tempname, statbuf[ST_MODE] & 07777)    except os.error, msg:        err('%s: warning: chmod failed (%r)\n' % (tempname, msg))    # Then make a backup of the original file as filename~    try:        os.rename(filename, filename + '~')    except os.error, msg:        err('%s: warning: backup failed (%r)\n' % (filename, msg))    # Now move the temp file to the original file    try:        os.rename(tempname, filename)    except os.error, msg:        err('%s: rename failed (%r)\n' % (filename, msg))        return 1    # Return succes    return 0  from tokenize import tokenprog match = {'if':':', 'elif':':', 'while':':', 'return':'\n', \         '(':')', '[':']', '{':'}', '`':'`'} def fixline(line):    # Quick check for easy case    if '=' not in line: return line     i, n = 0, len(line)    stack = []    while i < n:        j = tokenprog.match(line, i)        if j < 0:            # A bad token; forget about the rest of this line            print '(Syntax error:)'            print line,            return line        a, b = tokenprog.regs[3] # Location of the token proper        token = line[a:b]        i = i+j        if stack and token == stack[-1]:            del stack[-1]        elif match.has_key(token):            stack.append(match[token])        elif token == '=' and stack:            line = line[:a] + '==' + line[b:]            i, n = a + len('=='), len(line)        elif token == '==' and not stack:            print '(Warning: \'==\' at top level:)'            print line,    return line if __name__ == "__main__":    main()