Python Homework - creating a new list

Question

The assignment:

Write a function called splitList(myList, option) that takes, as input, a list and an option, which is either 0 or 1. If the

Answer 1

My previous answer was incorrect, and I really should have tested before I opened my mouth... Doh!!! Live and learn...

edit

your traceback is giving you the answer. It is reading the list as an args list. Not sure if there is a super pythonic way to get around it, but you can use named arguments:

splitList(myList=yourList)

OR

splitList(myList=(1,2,3))

OR

splitList(myList=[1,2,3])

But your problem is really probably

splitList(1,2,3,4)  # This is not a list as an argument, it is a list literal as your 'args' list

Which can be solved with:

splitList([1,2,3,4])

OR

splitList((1,2,3,4))

Is this the traceback you get?

Traceback (most recent call last):
  File "pyTest.py", line 10, in <module>
    print splitList(aList,1)
TypeError: splitList() takes exactly 1 argument (2 given)

The error is most likely telling you the issue, this would be that the method only takes one argument, but I tried passing in two arguments like your requirements state.

Answer 2

edit

Can you show the code where you are calling the splitList method?

this was incorrect

myList [i]

is your problem, you can't have a space in there. python is VERY VERY VERY strict about syntax

since people seemed to think they should downvote me, let me explain:

by having that space, you effectively said myList (which is a list), and [i], which is a list literal with the value of 'i' at index 0....

so you are passing two variables (one actual variable and one literal) into the append method, NOT separated by a comma, which will not work.

Answer 3

Henry Keiter's comment was correct. Just add one space before newlist.append(myList [i]) and it works just fine.

Alternatively, if your teacher lets you, you could use tabs instead of spaces to avoid this problem altogether (just make sure you don't use both in the same file).

Answer 4

def splitList(myList, option):
    return [i for i in myList if i<0] if option==0 else [i for i in myList if i>0]


# test
>>> myList=[2, 3, -1, 4, -7]
>>> splitList(myList, 0)
[-1, -7]
>>> splitList(myList, 1)
[2, 3, 4]
>>> 

Answer 5

As I mentioned in my comment, you should standardize your indentation: four spaces is Python standard. You can usually set your editor to insert four spaces instead of tabs (don't want to mix tabs with spaces, either).

As to your actual question: try writing three total functions: one that returns all the negative values, one that returns even values, and one that calls the appropriate function based on option.

def splitlist(myList, option):
    if option == 1:
        return get_even_elements(myList)
    elif option == 0:
        return get_negative_elements(myList)

def get_even_elements(myList):
    pass # Implementation this method here.

def get_negative_elements(myList):
    pass # Implementation this method here.

# Test it out!
alist = [-1, 2, -8, 5]
print splitlist(alist, 0)
print splitlist(alist, 1)

Answer 6

I tried your code as-is and I did not get any errors when I passed in a list of positive integers, so I don't know why your program is 'crashing', so I suspect something else is interfering with your debugging. (Although, as others have said, you really should use the same number of spaces at every indent level.)

Here's what I entered:

def splitList(myList):
    newlist = []
    for i in range(len(myList)):
        if (myList[i]%2 == 0):
           newlist.append(myList [i])  # Only 3-space indent here
    return newlist

print splitList([1, 2, 3, 4, 5])

When I run it:

[2, 4]

Can you show how you're invoking the method and the exact error message?