convert cosine similarity distance to confidence percent

Question

I am working to features of images based on deep learning techniques, and for labeling images, I specify the desired label with a threshold using cosine distance. The algorithm is as follows:

import math
from itertools import izip

def dot_product(v1, v2):
    return sum(map(lambda x: x[0] * x[1], izip(v1, v2)))

def cosine_measure(v1, v2):
    prod = dot_product(v1, v2)
    len1 = math.sqrt(dot_product(v1, v1))
    len2 = math.sqrt(dot_product(v2, v2))
    return prod / (len1 * len2)

Suppose I get the number 0.34. How do I convert this number to a percentage?