How to add elements to a List in python?

Question

I'm working on this task in python, but I'm not sure if I'm adding the elements to a list the right way. So basically I'm suppose to create a create_list function the takes the size of the list and prompt the user for that many values and store each value into the list. The create_list function should return this newly created list. Finally the main() function should prompt the user for the number of values to be entered, pass that value to the create_list function to set up the list, and then call the get_total function to print the total of the list. Please tell me what I'm missing or doing wrong. Thank you so much in advance.

def main():
    # create a list
    myList = []

    number_of_values = input('Please enter number of values: ')

    # Display the total of the list  elements.
    print('the list is: ', create_list(number_of_values))
    print('the total is ', get_total(myList))

    # The get_total function accepts a list as an
    # argument returns the total sum of the values in
    # the list

def get_total(value_list):

    total = 0

    # calculate the total of the list elements
    for num in value_list:
        total += num

    #Return the total.
    return total

def create_list(number_of_values):

    myList = []
    for num in range(number_of_values):
        num = input('Please enter number: ')
        myList.append(num)

    return myList

main()

Answer 1

In main you created empty list, but didn't assign create_list result to it. Also you should cast user input to int:

def main():
    number_of_values = int(input('Please enter number of values: '))  # int

    myList = create_list(number_of_values)  # myList = function result
    total = get_total(myList)

    print('the list is: ', myList)
    print('the total is ', total)

def get_total(value_list):
    total = 0
    for num in value_list:
        total += num
    return total

def create_list(number_of_values):
    myList = []
    for _ in range(number_of_values):  # no need to use num in loop here
        num = int(input('Please enter number: '))  # int
        myList.append(num)
    return myList

if __name__ == '__main__':  # it's better to add this line as suggested
    main()

Answer 2

You must convert inputs to integer. input() returns a string object. Just do

number_of_values = int(input('Please enter number of values: '))

And with every input you want to use as integer.

Answer 3

First Problem is you are not passing myList to create_list function, so myList inside of main is not going to get updated.

If you want to create a list inside the function and return it, and then get a total for that list, you need to first store the list somewhere. parse the inputs as integer, also, always do if __name__ == '__main__':. The Following code should work and print the correct result :)

def main():
    number_of_values = int(input('Please enter number of values: '))
    myList = create_list(number_of_values)
    print('the list is: ', myList)
    print('the total is ', get_total(myList))

def get_total(value_list):
    total = 0
    for num in value_list:
        total += num
    return total

def create_list(number_of_values):
    myList = []
    for num in range(number_of_values):
        num = int(input('Please enter number: '))
        myList.append(num)
    return myList
if __name__ == '__main__':
    main()

Answer 4

An alternative method to the posted solutions could be to have one function that creates your said list and finds the total of that list. In the solution, the map function goes through all the values given to it and only keeps the integers (The split method is used to remove commas and spaces from the values). This solution will print your list and values, but will not return any said value, so it will produce a NoneType, if you were to examine the function at the end.

    def main():
        aListAndTotal()

        #Creates list through finding the integers and removing the commas
        #For loop iterates through list and finds the total
        #Does not return a value, but prints what's stored in the variables

    def aListAndTotal():
        myList = map(int, input("Please enter number of values: ").split(","))
        total = 0
        for num in myList:
            total += num
        print ("The list is: ", myList)
        print ("The total is: ", total)

    if __name__ == "__main__":
        main()

Answer 5

List is one of the most important data structure in python where you can add any type of element to the list.

a=[1,"abc",3.26,'d']

To add an element to the list, we can use 3 built in functions:
a) insert(index,object)
This method can be used to insert the object at the preferred index position.For eg, to add an element '20' at the index 1:
     a.index(1,20)
Now , a=[1,20,'abc',3.26,'d']

b)append(object)
This will add the object at the end of the list.For eg, to add an element "python" at the end of the list:
    a.append("python")
Now, a=[1,20,'abc',3.26,'d','python']

c)extend(object/s)
This is used to add the object or objects to the end of the list.For eg, to add a tuple of elements to the end of the list:
b=(1.2, 3.4, 4.5)
a.extend(b)
Now , a=[1,20,'abc',3.26,'d','python',1.2, 3.4, 4.5]

If in the above case , instead of using extend, append is used ,then:
a.append(b)
Now , a=[1,20,'abc',3.26,'d','python',(1.2, 3.4, 4.5)]
Because append takes only one object as argument and it considers the above tuple to be a single argument that needs to be appended to the end of the list.

Answer 6

You need to assign the return value of create_list() to a variable and pass that into get_total()

myList = create_list()
total = get_total(myList)

print("list " + str(myList))
print("total " + str(total))

Answer 7

Adding an element to an existing list in python is trivial. Assume who have a list names list1

>>> list1 = ["one" , "two"]

>>> list1 = list1 + "three"

this last command will add the element "three" to the list. This is really simple, because lists are objects in python. When you print list1 you get:

["one" , "two" , "three"]

Done