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eqfix.py
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#! /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 sys import re import os from stat import * import string err = sys.stderr.write dbg = err rep = 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()