Python Forum

I've been working a problem in another forum and ran across something I don't understand.
Giving a list of numbers as input and then removing the numbers that are less than or equal to a boundry,
can't seem to get all numbers to be removed. Any help understanding why the numbers are not removed would be great.
The numbers is usually the second in the list.

boundry = 10
numbers = list(map(int, input('>> ').split(',')))

print(f'list -> {numbers}')

for number in numbers:
    if number <= boundry:
        print(f'removed number -> {number}')
        numbers.remove(number)

print(f'Numbers left -> {numbers}')

Output:

Output:
>> 3,5,8,14,10
list -> [3, 5, 8, 14, 10]
removed number -> 3
removed number -> 8
removed number -> 10
Numbers left -> [5, 14]

As you can see, 3,8,10 are removed, but not 5.

I found a solution.
Had to reverse the list and keep index positions.

boundry = 10
numbers = list(map(int, input('>> ').split(',')))

print(f'list -> {numbers}')

for number in reversed(range(len(numbers))):
    if numbers[number] <= boundry:
        print(f'removed number -> {numbers[number]}')
        del numbers[number]

print(f'Numbers left -> {numbers}')

Output:
>> 3,5,8,14,22,9
list -> [3, 5, 8, 14, 22, 9]
removed number -> 9
removed number -> 8
removed number -> 5
removed number -> 3
Numbers left -> [14, 22]

You shouldn't alter a list that you are iterating over, iterate over a copy of the list and alter the original list.

for number in numbers[:]:

I prefer building a new list that only contains the values I want to keep.

boundry = 10
numbers = list(map(int, input('>> ').split(' ')))
kept = [number for number in numbers if number > boundry]
print('Numbers >', boundry, '=', kept)

This is the solution I gave but, just seems there are better ways. Doesn't work if the list is not sorted first. Was trying to keep the original alignment eg(3,6,2,22) so to speak. Think I still get incorrect placement from time to time.

boundry_dict = {} # Create a dict to hold key/value
boundry_num = 10 # Boundry starts at 10
numlist = [] # A list to hold the numbers

numbers = list(map(int, input('>> ').split(','))) # Get input separated by comma
numbers.sort() # Sort the numbers in case not sequenced
# Loop through the input
for number in numbers:
    if number <= boundry_num: # If a number is less than boundry append to list
        numlist.append(number)
    else: # If all numbers less than boundry then increase boundry by 10
        boundry_num += 10
        numlist = [] # Clear the list
        numlist.append(number) if number <= boundry_num else False # Without this it will miss a number
    boundry_dict[boundry_num] = numlist # Add the boundry number and list to dict

# Loop through the dict and display
for key, value in boundry_dict.items():
    print(f'Group of {key}\'s: {value}')

output

Output:
>> 12,5,9,6,22,40,42
Group of 10's: [5, 6, 9]
Group of 20's: [12]
Group of 30's: [22]
Group of 40's: [40]
Group of 50's: [42]