[Tutor] HELP PLEASE

[Cameron Simpson]

On 12Aug2019 15:11, Marissa Russo <mrusso11 at u.rochester.edu> wrote:
>This is my code:

Thank you.

>This is the output of my updated code:
>Traceback (most recent call last):
>  File "/Applications/Python 3.7/exercises .py", line 37, in <module>
>    main()
>  File "/Applications/Python 3.7/exercises .py", line 33, in main
>    m = mean(data[0])
>  File "/Applications/Python 3.7/exercises .py", line 29, in mean
>    return(sum(nums)/len(nums))
>TypeError: unsupported operand type(s) for +: 'int' and 'str'

Thank you for this as well, it makes things much clearer.

So, to your code:

>import math

Just a remark: you're not using anything from this module. I presume you 
intend to later.

>def get_numbers():
>    print("This program will compute the mean and standard deviation")
>    file1 = input("Please enter the first filename: ")
>    file2 = input("Please enter the second filename: ")
>    x = open(file1, "r")
>    y = open(file2, "r")
>    nums = x.readlines()
>    nums2 = y.readlines()

As has been mentioned in another reply, readlines() returns a list of 
strings, one for each line of text in the file.

In order to treat these as numbers you need to convert them.

>    return nums, nums2
>
>def to_ints(strings):
>    num_copy = []
>    for num in nums:
>        num_copy.append(float(num))
>    return num_copy

This returns a list of floats. You might want to rename this function to 
"to_floats". Just for clarity.

>    return to_ints(nums), to_ints(nums2)

This isn't reached. I _think_ you need to put this line at the bottom of 
the get_numbers function in order to return two lists of numbers. But it 
is down here, not up there.

>def mean(nums):
>    _sum = 0
>    return(sum(nums)/len(nums))

This is the line raising your exception. The reference to "+" is because 
sum() does addition. It starts with 0 and adds the values you give it, 
but you're handing it "nums".

Presently "nums" is a list of strings, thus the addition of the initial 
0 to a str in the exception message.

If you move your misplaced "return to_ints(nums), to_ints(nums2)" 
statement up into the get_numbers function you should be better off, 
because then it will return a list of numbers, not strings.

Cheers,
Cameron Simpson <cs at cskk.id.au>