Python Snippet - Pearson Correlation function

Here's the code I wrote in Python to calculate the Pearson Correlation. It works just like the Java version.

def get_Pearson_Correlation(dataseries1, dataseries2):
    result = 0.0
    sum_sq_x = 0.0
    sum_sq_y = 0.0
    sum_coproduct = 0.0
    mean_x = dataseries1[0]
    mean_y = dataseries2[0]

    for i in range(2,len(dataseries1)+1):
        sweep = (i-1)/float(i)
        delta_x = dataseries1[i-1]-mean_x
        delta_y = dataseries2[i-1]-mean_y
        sum_sq_x += delta_x * delta_x * sweep
        sum_sq_y += delta_y * delta_y * sweep
        sum_coproduct += delta_x * delta_y * sweep
        mean_x += delta_x / float(i)
        mean_y += delta_y / float(i)

    pop_sd_x = (sum_sq_x / float(len(dataseries1)))**0.5
    pop_sd_y = (sum_sq_y / float(len(dataseries1)))**0.5
    cov_x_y = sum_coproduct / float(len(dataseries1))

    result = cov_x_y / (pop_sd_x*pop_sd_y)

    return result