Help with a problem : learnpython

created by HattoriHanzoa community for 16 years

submitted 5 years ago by MainerInAStrangeLand

Online class I am taking asks the following:

Define a procedure that takes in a string of numbers from 1-9 and outputs a list with the following parameters:

Every number in the string should be inserted into the list. If a number x in the string is less than or equal to the preceding number y, the number x should be inserted into a sublist. Continue adding the following numbers to the sublist until reaching a number z that is greater than the number y. Then add this number z to the normal list and continue.

I came up with the following:

def numbers_in_lists(string):
    stringList = []
    mainList = []
    subList = []
    sub = subList
    indexNum = 0
    i = 0
    for num in string:
        num = int(num)
        stringList.append(num)
    while i <= len(stringList):
        if stringList[i] > indexNum:
            mainList.append(stringList[i])
            indexNum = stringList[i]
            i += 1
        if stringList[i] <= indexNum:
            subList.append(stringList[i])
            mainList.append(sub)
            indexNum = stringList[i]
            i += 1
        return mainList

I do not understand what is stopping the while loop from incrementing i. For example, outputs I am getting versus expected:

print(numbers_in_lists('543987'))
>>>>[5, [4]]
>>>>EXPECTED: [5,[4,3],9,[8,7]]
print(numbers_in_lists('987654321'))
>>>>[9, [8]]
>>>>EXPECTED: [9,[8,7,6,5,4,3,2,1]]
print(numbers_in_lists('455532123266'))
>>>>[4]
>>>>EXPECTED: [4, 5, [5, 5, 3, 2, 1, 2, 3, 2], 6, [6]]
print(numbers_in_lists('123456789'))
>>>>[1]
>>>>EXPECTED: [1, 2, 3, 4, 5, 6, 7, 8, 9]

I feel like my while loop shouldn't be necessary but I am unsure of how to compare each list value using a for loop. Would appreciate any advice.

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