Change all xrefs in Autocad Drawings

This recipe (from Activestate) for Autodesk Autocad is a script which asks for a base directory and then changes all xrefs in all drawings in all subdirectories so that they use relative paths. To use it just copy it somewhere in your target directory structure and run.

# Relative-refs.pyw
"""A short python script for repathing xrefs in Autocad."""

import win32com.client,os, os.path, tkFileDialog
from Tkinter import *
from tkMessageBox import askokcancel
from time import sleep

# Get a COM object for Autocad
acad = win32com.client.Dispatch("AutoCAD.Application")

def repath(filename):
    print 'Repathing %s...' %filename
    doc = acad.Documents.Open(filename)
    
    blocks = doc.Database.Blocks # Internally xrefs are just blocks!
    xrefs = [item for item in blocks if item.IsXRef]
    
    if xrefs:
        for xref in xrefs:
            old_path = xref.Path
            new_path = os.path.join('..\\x-ref\\',os.path.basename(old_path))
            xref.Path = new_path
            print 'Old path name was %s, new path name is %s.\n' %(old_path, new_path)
    try:
        doc.Close(True) # Close and save
    except: # Something when wrong,
        doc.Close(False) # close then report it
        raise
    
class Logger:
    """A filelike object that prints its input on the screen."""
    
    def __init__(self, logfile=None):
        """Takes one argument, a file like object for logging."""
        print 'Starting logger...'
        if not logfile:
            self.logfile = open('relative-refs.log','w')
        else:
            self.logfile = logfile
        sys.stderr = self                 # Super cheap logging facility...
        sys.stdout = self                 # Just redirect output to a file.
        print 'Logger running...'
    
    def write(self, line):
        sys.__stdout__.write(line)
        self.logfile.write(line)
    
    def close(self):
        """The close method restores stdout and stderr to normal."""
        self.logfile.close()
        sys.stderr = sys.__stderr__
        sys.stdout = sys.__stdout__

class Tktextfile:
    """A file like interface to the Tk text widget."""
    
    def __init__(self, root):
        """Create a scrollable text widget to be written to."""
        self.root = root
        self.text = Text(root,width=40,height=20)
        self.text.pack(side=LEFT, expand=True, fill=BOTH)
        scrollbar = Scrollbar(root)
        scrollbar.pack(side=RIGHT,fill=Y)
        self.text.configure(yscrollcommand=scrollbar.set)
        scrollbar.config(command=self.text.yview)
        self.text.focus()
    
    def write(self, line):
        """Write method for file like widget."""
        self.text.insert(INSERT, line)
        self.text.see(END)
    
    def close(self):
        """Fake close method."""
        pass

if __name__ == '__main__':
    if acad.Visible:
        acad.Visible = False
    root = Tk()
    text = Tktextfile(root)
    logger = Logger(text)
    dir = tkFileDialog.askdirectory()

    answer = askokcancel('RePath','Re path all dwg files in ' + dir + '?')
    
    if answer:
        for dirpath, subdirs, files in os.walk(dir):
            for name in files:
                ext = name.split('.')[-1] or ''
                # We want dwg files which are not in the x-ref directory
                if ext.lower() == 'dwg' and 'x-ref' not in dirpath.lower():
                    drawing = os.path.join(dirpath, name)
                    try:
                        repath(drawing)
                    except:
                        print 'Unable to repath drawing %s!' %drawing
                root.update()
    acad.Visible = True

There is also another example on Activestate, which casts Python objects as the correct Autocad type via win32com.client.CastTo(item)