ip parser with err check

#  parse ipv4 stirng into a returned list of numbers, or -1 if there is an input err
# JGMiner June 2014   v3:Jan 2015

def addr2ints(s):
    a=[-1]  # in order to catch dots with no digits will initialze negitive
    for d in s:
        if d.isdigit() : 
           if a[-1]==-1 : a[-1] += 1
           a[-1]=a[-1]*10+int(d)
           if a[-1]>255 : return [-1] #catch too large input
        elif d =='.' :
            if a[-1]==-1 : return [-1]
            a.append(-1)      
        else : return [-1]     # Not valid addr        
    if len(a) != 4 or a[-1] == -1 : return [-1]
    return a

# TEST HARNESS and TEST PATTERNS BELOW ================

def testa2i(s): #tests the function above : addr2ints
    print    
    print "test input :",s
    a=addr2ints(s)
    print "list of integers from function: ", a
    print "python string split to list of strings: ", str.split(s,'.')

#test coverage list 
testa2i("192.1.223.5")
testa2i("34.123")
testa2i("34.56.78.90.12")
testa2i("23..12.3")
testa2i("23.0.13.3")
testa2i("2.3.255.1")
testa2i("192.323.223.5")
testa2i("192.-45.14.3")
testa2i("192,1.23.5")
testa2i("19w2.1.23.5")
testa2i("....")
testa2i("...")
testa2i(".")
testa2i("12345678901234567890")

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