How to remove unwanted numbers from the list?

Question

I have this below code written to remove numbers greater than 5 from the list. But it does not work though the code looks fine to me. I'm new to python and trying to get my basics right. I decided to use remove since i'm checking based on the value

a = [1,5,4,6,3,8,9,5,9] 
for i in a:
    print (i)
    if i<=5:
        continue
    a.remove(i)
print (a)

Result - [1, 5, 4, 3, 5, 9]

Interesting. What happens if you use `for i in reversed(a):` instead of `for i in a:`? — wim, Nov 01 '18 at 17:19
You can use array for making your life simpler. `a = np.array([1,5,4,6,3,8,9,5,9])` and then `a = a[a<5]` will give you what you want — Sheldore, Nov 01 '18 at 17:22
Or with a list comprehension: `a = [c for c in a if c <= 5 ]` — Jongware, Nov 01 '18 at 17:23
Or with [`filter`](https://docs.python.org/3/library/functions.html#filter): `filter(lambda x: x<=5, a)` — Jongware, Nov 01 '18 at 17:37

score 0 · Answer 1 · answered Nov 01 '18 at 17:19

0

it will not work because you are removing item from list while iterating the same one....so when you remove an element, next iteration you will jump one one them.

Solution: 1) use 2 array; 2) use a while loop and when you remove an element you decrease the len of the array and you don't increment the iteration

a = [1,5,4,6,3,8,9,5,9]
i=0
l=len(a)
while i<l:
    if a[i]>5:
        a.pop(i)
        l-=1
    else:
        i+=1
print (a)

Result:

[1, 5, 4, 3, 5]

answered Nov 01 '18 at 17:19

Carlo 1585

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how does it work when i use reversed(a) in my code. I thought it would skip based on the above explanation – Py_learner Nov 01 '18 at 17:37
https://www.programiz.com/python-programming/methods/built-in/reversed – Carlo 1585 Nov 01 '18 at 17:40

How to remove unwanted numbers from the list?

1 Answers1