def getEditDist(str1, str2):
    """ return edit distance between two strings of equal length 
    >>> getEditDist("HIHI", "HAHA")
    2
    """
    assert(len(str1)==len(str2))
    str1 = str1.upper()
    str2 = str2.upper()

    editDist = 0
    for c1, c2 in zip(str1, str2):
        if c1!=c2:
            editDist +=1
    return editDist