# commonprefix.py

# commonprefix.py

from os.path import commonprefix
v = commonprefix('outstanding outside outshines outspoken'.split())
print v

# longestcommonprefix.py

zzz = '''
hello
world
forecastable
specialxyz
xyz
foresight
shortabcdefghijklmnopqrstuvwxyz
longestprefix
shortest
shortage
longestxyz
long
foretold
forever
alpha
foreign
speciality
beta
longestabc
short
zebra
forego
abc
shortxyz
'''.splitlines()

def lcp(L):
    longest = [0, []]
    vL = 0
    if len(L)>1:
        sL = sorted(L)
        v2 = ''
        for i in range(len(L)-1):
            v = commonprefix(sL[i:i+2])
            if v:
                vL = len(v)
                v2 = v
            else:
                if longest[0] == vL:
                    if v2 not in longest[1]:
                        longest[1].append(v2)
                elif longest[0] < vL:
                    longest = [vL, [v2]]
    return longest[-1]
0
print lcp(zzz)