Python version of https://gist.github.com/3773519 that pulls all bookmarks on the first sync, and does incremental updates afterwards. Also uses the Mac OS X keychain to retrieve your password so it doesn't need to live in a file on your computer in plain text.

allpinboard.py

#!/usr/bin/env python

"""
Requirements:

* pytz
* requests
* dateutil

You should edit the username, bookmark_filename, and local_timezone variables
to suit your preferences.
"""

from datetime import datetime
import subprocess
import os

import pytz
import requests
from dateutil import parser as date_parser

keychain_process = subprocess.Popen(["security", "find-internet-password", "-s", "pinboard.in", "-w"], stdout=subprocess.PIPE)
trim_newlines = subprocess.Popen(["tr", "-d", "'\n'"], stdin=keychain_process.stdout, stdout=subprocess.PIPE)
keychain_process.stdout.close()
password, _ = trim_newlines.communicate()

username = "dlo"
bookmark_format = u"<a href='{href}' title='{extended}'>{description}</a>"
bookmark_filename = "~/Dropbox/PinboardBookmarks.html"
local_timezone = "America/Los_Angeles"
basic_auth = (username, password)

url = None
try:
    timestamp = os.stat(bookmark_filename).st_mtime
except OSError:
    url = "https://api.pinboard.in/v1/posts/all?format=json"
else:
    last_modified_local_time = datetime.fromtimestamp(timestamp, pytz.timezone(local_timezone))
    last_modified = last_modified_local_time.astimezone(pytz.timezone("UTC"))

    # Check if bookmarks have been updated remotely since last local update
    response = requests.get("https://api.pinboard.in/v1/posts/update?format=json", auth=basic_auth)
    last_modified_on_server = date_parser.parse(response.json()['update_time'])

    if last_modified_on_server > last_modified:
        url = "https://api.pinboard.in/v1/posts/all?format=json&fromdt={}".format(last_modified.strftime("%FT%TZ"))
finally:
    if url is not None:
        response = requests.get(url, auth=basic_auth)
        with open(bookmark_filename, 'a') as bookmark_file:
            for bookmark in response.json():
                bookmark_file.write(bookmark_format.format(**bookmark).encode("utf-8"))