Appending Elements of a String into a List (python)

Question

This program is designed to take a string consisting of numbers (any length) and outputting the contents of the string into a list, one digit at a time. Should a number, x, be less than or equal to the preceding number, y, the number x is to be inserted into a sublist. Until a number, z, is greater than y, everything between x and z will also be added to the sublist. Here is the code

def numbers_in_lists(string):
    final = []
    temp = []
    prev = 0

    for i in range(len(string)):
        value = int(string[i])

        if value<=prev:
            temp.append(value)
        else:
            if temp != []:
                final.append(temp)
                temp = []
            final.append(value)
            prev = int(string[i])

    print final
    return final

To test this function, add the following to the remainder of the code:

string = '543987'
result = [5,[4,3],9,[8,7]]
print repr(string), numbers_in_lists(string) == result
string= '987654321'
result = [9,[8,7,6,5,4,3,2,1]]
print repr(string), numbers_in_lists(string) == result
string = '455532123266'
result = [4, 5, [5, 5, 3, 2, 1, 2, 3, 2], 6, [6]]
print repr(string), numbers_in_lists(string) == result
string = '123456789'
result = [1, 2, 3, 4, 5, 6, 7, 8, 9]
print repr(string), numbers_in_lists(string) == result

After the code creates and returns a sublist, it finds a new maximum value and doesn't add anything else to the list, thus leaving the final list incomplete.

If I test with the string '543987' the prefered result is [5,[4,3],9,[8,7]] whereas my result is [5,[4,3],9]

Updated the end of the question since it wasn't clear. Basically, the list doesn't fill itself out, it just stops on the iteration after it finishes a sublist. — Σqu
– Σqu, Commented Jun 14, 2017 at 6:07

themiurge · Accepted Answer · 2017-06-14 06:21:46Z

2

You need to check temp after the for loop ends, it might still contain something:

def numbers_in_lists(string):
    final = []
    temp = []
    prev = 0

    for digit in string:
        value = int(digit)

        if value<=prev:
            temp.append(value)
        else:
            if temp:
                final.append(temp)
                temp = []
            final.append(value)
            prev = int(digit)

    if temp:
        final.append(temp)

    print final
    return final

I also slightly re-worked your for loop (no need to use indexed access) and replaced temp != [] with temp (see here).

answered Jun 14, 2017 at 6:21

themiurge

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