I have a question about While loops

[imish06]

This is the question:

"The user must enter a non-negative number to add to the lists or a negative number to stop the program. For every non-negative number entered, place each even and odd number in its respective list. Print the lists of even and odd numbers at the end of the program. You must use a while loop."

This is my code and algorythm:

#create empty lists to hold even and odd numbers
even = ""
odd = ""
#create a message giving the directions
mess = "Enter a non-negative number to add to the lists or a negative number to stop"
#get input from the user
val = raw_input(mess)
#while input does not equal sentinal
while (val > 0):
    #process the data using if statements
    if ((val%2) == 0):
        even = even + val
    else:
        odd = odd + val
    #get next value
    val = raw_input(mess)
#print lists
print even
print odd
 

I keep getting an error message when I run the program. Does anybody know what is wrong?

[bvdet]

This is the question:

"The user must enter a non-negative number to add to the lists or a negative number to stop the program. For every non-negative number entered, place each even and odd number in its respective list. Print the lists of even and odd numbers at the end of the program. You must use a while loop."

This is my code and algorythm:

#create empty lists to hold even and odd numbers
even = ""
odd = ""
#create a message giving the directions
mess = "Enter a non-negative number to add to the lists or a negative number to stop"
#get input from the user
val = raw_input(mess)
#while input does not equal sentinal
while (val > 0):
    #process the data using if statements
    if ((val%2) == 0):
        even = even + val
    else:
        odd = odd + val
    #get next value
    val = raw_input(mess)
#print lists
print even
print odd
 

I keep getting an error message when I run the program. Does anybody know what is wrong?

raw_input() returns a string. You must convert the string to an integer. You mentioned lists. You are initializing two strings, but you should initialize two lists.

aList = []

To add list elements, use the list method append().

[imish06]

raw_input() returns a string. You must convert the string to an integer. You mentioned lists. You are initializing two strings, but you should initialize two lists.

aList = []

To add list elements, use the list method append().

I tried that and it didn't work. I keep getting the same message: "not all arguments converted during string formatting."

#creat empty lists to hold even and odd numbers
even = []
odd = []
#create a message giving the directions
mess = "Enter a non-negative number to add to the lists or a negative number to stop"
#get input from the user
val = raw_input(mess)
#while input does not equal sentinal
while (x > 0):
    #process the data using if statements
    if(x%2 ==0):
        even.append(val)
    else:
        odd.append(val)
    #get next value
    val = raw_input(mess)
#print lists
print even
print odd

[Laharl]

You need to use input() (or int(raw_input()) ), since raw_input gives you a string. The % operator, when applied to strings, is the string formatting operator, used like this:

str = '%d+%d=%d' % (1, 1, 2)
print str #Prints 1+1=2
 

Thus, Python thinks you're trying to format a string when you're really trying to use modulus on an integer.

[bvdet]

As I said:
raw_input() returns a string. You must convert the string to an integer.

[boxfish]

Are you familliar with different variable types in Python? raw_input returns a string. For example, let's say you enter 3. Then without converting it to an int, val will hold the string "3". Since it is a string, you will get very strange results if you treat it like a number. For example, val * 5 is "33333". Five threes. So you need to convert it to an integer with the int function:

val = int(raw_input(mess))
 

Because "3" is not the same as 3.
Hope this makes a whole lot of sense. :-) Good luck.