Contents
shopping = ["potatoes", "pears", "coffee", "grapes", "peas", "bananas",
            "bleach", "toothpaste", "apples", "pesto", "pasta", "wine", "cabbage"]

L = len(shopping)
for i in range(L):
    for j in range(i, L):
        if len(shopping[i]) > len(shopping[j]):
            maxlen = len(shopping[j])
        else:
            maxlen = len(shopping[i])
        k = 0
        while shopping[i][k] == shopping[j][k] and k < maxlen-1:
            k = k+1
        if shopping[i][k] > shopping[j][k]:
            tmp = shopping[i]
            shopping[i] = shopping[j]
            shopping[j] = tmp
            
print(shopping)