Modulo operation difference between Swift and Python

Question

I am trying to port a modular inverse operation from Python to Swift, and my modulo operation is producing different results. I am wondering if someone can point out why I am getting different results? I am using this as my BInt Library.

PYTHON CODE:

def inverse(x, p):
"""
Calculate the modular inverse of x ( mod p )

the modular inverse is a number such that:

(inverse(x, p) * x) % p  ==  1 

you could think of this as: 1/x
"""
inv1 = 1
inv2 = 0
print "first x = %d" % x
print "first p = %d" % p
while p != 1 and p!=0:
    inv1, inv2 = inv2, inv1 - inv2 * (x / p)
    print "inv1 = %d" % inv1
    print "inv2 = %d" % inv2
    x, p = p, x % p
    print "x = %d" % x
    print "p = %d" % p

return inv2

SWIFT CODE:

func inverse(b: BInt, n: BInt) -> BInt {

    var inv1 = BInt(1)
    var inv2 = BInt(0)
    var p = n
    var x = b
    print("first x = \(x)")
    print("first p = \(p)")
    while p != 1 && p != 0 {
        var temp = inv2
        inv2 = inv1 - inv2 * (x/p)
        inv1 = temp
        print("inv1 = \(inv1)")
        print("inv2 = \(inv2)")
        temp = p
        p = x % p
        x = temp
        print("x = \(x)")
        print("p = \(p)")
    }
    return inv2
}

Python results:

first x = -34499628904269660561674201530767158034393542375844615658184142552908072257357
first p = 115792089237316195423570985008687907853269984665640564039457584007908834671663
inv1 = 0
inv2 = 1
x = 115792089237316195423570985008687907853269984665640564039457584007908834671663
p = 81292460333046534861896783477920749818876442289795948381273441455000762414306
inv1 = 1
inv2 = -1
x = 81292460333046534861896783477920749818876442289795948381273441455000762414306
p = 34499628904269660561674201530767158034393542375844615658184142552908072257357
inv1 = -1
inv2 = 3
x = 34499628904269660561674201530767158034393542375844615658184142552908072257357
p = 12293202524507213738548380416386433750089357538106717064905156349184617899592

Swift results:

first x = -34499628904269660561674201530767158034393542375844615658184142552908072257357
first p = 115792089237316195423570985008687907853269984665640564039457584007908834671663
inv1 = 0
inv2 = 1
x = 115792089237316195423570985008687907853269984665640564039457584007908834671663
p = -34499628904269660561674201530767158034393542375844615658184142552908072257357
inv1 = 1
inv2 = 3
x = -34499628904269660561674201530767158034393542375844615658184142552908072257357
p = 12293202524507213738548380416386433750089357538106717064905156349184617899592
inv1 = 3
inv2 = 7
x = 12293202524507213738548380416386433750089357538106717064905156349184617899592
p = -9913223855255233084577440697994290534214827299631181528373829854538836458173