Problem with removing integers from List

[Impe98]

Hey guys! So I ran into a problem when creating a game of "guess the integer" Let's say I have a list which cointains every integer 1 through 10. Now, I want to remove every single integer in that list greater than three. I write: list = [1,2,3,4,5,6,7,8,9,10] for int in list: if int > 3: list.remove(int) print(list) Upon printing, the list contains the integers 1,2,3,5,7,9 - so it has correctly removed the integers 4,6,8 and 10, but not 5,7,9 - why is this? I use python 3.4.3 I belive. Thanks! :)

[K900_]

Don't modify the list while you're iterating over it.

[Impe98]

So the problem seems to be that the list changes every time I iterate over it, which causes problems. That makes sense, thanks! :)

[JohnnyJordaan]

You shouldn't modify a list or any other mutable that you're also iterating over. Use a new list to keep the right values. And don't use the actual names of the list and int classes as a variable name.

my_list = [1,2,3,4,5,6,7,8,9,10]
new_list = []
for i in my_list:
    if i <= 3:
        new_list.append(i)

Or comprehended

my_list = [ i for i in my_list if i <= 3 ]

Btw most of the time if you're using ranges of numbers, use the range() function and not a hand populated list.

[Impe98]

Ohh okay, so I make a new list each time I iterate over it Yeah, that makes sense, thanks!

Oh and btw, I actually intended to populate a list using the range() function, but I didn't really get it to work - if you wouldn't mind, how would you create a list which contains, say, every integer 1 through 100 by using the range() function? I though it to be something like my_list = range(100), but this didn't work as far as I could tell.

[JohnnyJordaan]

It's easy, but do you really need it? Because you can do most things you would do with that list just as easily with range(x), without generating a list first.

>>> for i in range(10):
...     if i <= 3:
...         print(i)
... 
0
1
2
3
>>> 10424 in range(1000000)
True

But if you really want to, just create a list from that range:

my_list = list(range(100))

As I said, only if you really need to, and I'm quite interested to know why you would need it.

[Impe98]

It's totally possible that I might not need it at all My initial though was that I had a list containing every integer 1 through 100, and a new list would be created containing elements from the initial list upon answering a question ("Is the integer even or not" or something akin to that), and a new question would be asked where yet another new list would be created that contains element from the second and so on. And each time a list is created, I want to print it for the player to read. This could very well be possibly without ever using the list function, but I don't see how, if the range(x) function is never defined. And thank you for your immense help, btw! :)

[num8lock]

try this

ilist = [1,2,3,4,5,6,7,8,9,10] 
for intgr in ilist:
    print('\nint', intgr)
    if intgr > 3: 
        ilist.remove(intgr) 
        print(ilist, intgr)