struggling with these problems

Discussion in 'Python' started by su29090, Jan 30, 2013.

  1. su29090

    su29090 Guest

    1.Given that worst_offenders has been defined as a list with at least 6 elements, write a statement that defines lesser_offenders to be a new list that contains all the elements from index 5 of worst_offenders and beyond. Do not modify worst_offenders .

    I tried this but it didn't work:

    lesser_offenders = worst_offenders[5:6]

    2.Given a variable temps that refers to a list, all of whose elements refer to values of type float , representing temperature data, compute the average temperature and assign it to a variable named avg_temp . Besides temps and avg_temp , you may use two other variables -- k and total .

    I'm not sure about this one but this is what I have:

    for k in range(len(temps)):
    total += temps[k]

    avg_temp = total / len(temps)

    3.Associate the sum of the non-negative values in the list numbers with the variable sum .

    is it this:

    for numbers in sum:
    if sum +=?

    I'm confused at #3 the most

    i'm not doing it in python 3.2.3 it's called Myprogramminglab.
    su29090, Jan 30, 2013
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  2. su29090

    MRAB Guest

    Python uses half-open ranges (and counts from 0), which means that the
    start index is included and the end index is excluded.

    Therefore, worst_offenders[5:6] means the slice from index 5 up to, but
    excluding, index 6; in other words, an empty list.

    The question says "and beyond"; in Python you can just omit the end
    index to indicate everything up to the end.
    You didn't set the initial value of total, which is 0.
    Well, that's not valid Python.

    What you want to do is to add each number from the list to the sum only
    if it's non-negative, i.e. greater than or equal to 0.
    Have a look at Dive Into Python:
    MRAB, Jan 30, 2013
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  3. Er, no. It's a one-element list: index 5 is included, index 6 is excluded.

    py> L = list("abcdefgh")
    py> L[5:6]
    Steven D'Aprano, Jan 30, 2013
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