create Bitcoin public key from private key

public.py

#! /usr/bin/env python

class Point(object):
    def __init__(self, _x, _y, _order = None): self.x, self.y, self.order = _x, _y, _order

    def calc(self, top, bottom, other_x):
        l = (top * inverse_mod(bottom)) % p
        x3 = (l * l - self.x - other_x) % p
        return Point(x3, (l * (self.x - x3) - self.y) % p)

    def double(self):
        if self == INFINITY: return INFINITY
        return self.calc(3 * self.x * self.x, 2 * self.y, self.x)

    def __add__(self, other):
        if other == INFINITY: return self
        if self == INFINITY: return other
        if self.x == other.x:
            if (self.y + other.y) % p == 0: return INFINITY
            return self.double()
        return self.calc(other.y - self.y, other.x - self.x, other.x)

    def __mul__(self, e):
        if self.order: e %= self.order
        if e == 0 or self == INFINITY: return INFINITY
        result, q = INFINITY, self
        while e:
            if e&1: result += q
            e, q = e >> 1, q.double()
        return result

    def __str__(self):
        if self == INFINITY: return "infinity"
        return "04 %x %x" % (self.x, self.y)

def inverse_mod(a):
    if a < 0 or a >= p: a = a % p
    c, d, uc, vc, ud, vd = a, p, 1, 0, 0, 1
    while c:
        q, c, d = divmod(d, c) + (c,)
        uc, vc, ud, vd = ud - q*uc, vd - q*vc, uc, vc
    if ud > 0: return ud
    return ud + p

p, INFINITY = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2FL, Point(None, None) # secp256k1
g = Point(0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798L, 0x483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8L,
          0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141L)
secret =  0x2EE42A735AE3D0C1A7E435EF3B4731B0205A7839015E100BCC8472EE989EC887L
print '  privkey:    %x\n   pubkey: %s' % (secret, g * secret)