Rough outline of a Trie in Python, storing 10 digit numbers

gistfile1.py

import random

class Trie:
	def __init__(self):
		self.children = [None]*10
	def insert(self, i, n):
		if n == 1: 
			self.children[i] = True
		else:
			d = i / 10**(n-1)
			r = i % 10**(n-1)
			if not isinstance(self.children[d], Trie):
				self.children[d] = Trie()
			self.children[d].insert(r,n-1)
	def search(self, needle, num_digits=10):
		if num_digits == 1:
			return (self.children[needle] == True)
		else:
			d = needle / 10**(num_digits-1)
			if isinstance(self.children[d], Trie):
				r = needle % 10**(num_digits-1)
				return self.children[d].search(r, num_digits-1)
			else:
				return False
	def list(self, prefix=0):
		l = []
		for i in range(10):
			c = self.children[i]
			if c is not None:
				if isinstance(c, Trie):
					l.extend(c.list(prefix*10+i))
				else:
					l.append(prefix*10+i)
		return l
	def __str__(self):
		return str(self.list())

# sample 1,000,000 random 10-digit numbers
nums = random.sample(xrange(10**10), 1000000)

# insert them into trie
trie = Trie()
for num in nums:
	trie.insert(num, 10)

# test presence of a number
print len(trie.list())
print trie.search(nums[444])
print trie.search(9123456789)