Format the names of all symbols in a Sketch file to be all lowercase

format.py

import os
import zipfile
import tempfile
import sys
import json

zipname = sys.argv[1]
def format_symbol_name(name):
    return name.lower()

def update_file(zipname):
    # generate a temp file
    tmpfd, tmpname = tempfile.mkstemp(dir=os.path.dirname(zipname))
    os.close(tmpfd)

    # read the sketch file as a zip file      
    with zipfile.ZipFile(zipname, 'r') as zin:
        with zipfile.ZipFile(tmpname, 'w') as zout:
            zout.comment = zin.comment # preserve the comment

            # track how many layer names were changed
            updated = 0

            for item in zin.infolist():
                data = zin.read(item.filename)

                # find pages and update symbol names
                if item.filename.startswith('pages') and item.filename.endswith('.json'):
                    parsed_json = json.loads(data)
                    for layer in parsed_json['layers']:

                        # only modify symbol masters
                        if layer['_class'] == 'symbolMaster':
                            before_name = layer['name']
                            formatted_name = format_symbol_name(layer['name'])
                            layer['name'] = formatted_name

                            if before_name != formatted_name: updated += 1
                    data = json.dumps(parsed_json)

                #write back to temp archive
                zout.writestr(item, data)
            print '%d symbol names updated.' % updated
    # replace with the temp archive
    os.remove(zipname)
    os.rename(tmpname, zipname)

update_file(zipname)