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Recap
Iterating over a list
Modifying lists
10. Deleting list elements – part 2
Working with multiple lists
Congratulations

## Instruction

Okay. You could see that the method we wrote didn't work. How can we correctly remove all negative numbers from the list? The secret is to create a copy of the list. Take a look:

sleep_durations = [268, -590, -326, 506]
for duration in sleep_durations[:]:
if duration < 0:
sleep_durations.remove(duration)
print(sleep_durations)


Instead of iterating over sleep_durations, we created a temporary copy using sleep_durations[:]. The syntax [:] means "copy all elements from the list". When we use this, we iterate over a copy containing all the list elements in each iteration, but we remove items from the actual list. This gives us the correct algorithm.

## Exercise

As you can see, some erroneous data was inserted into Martha's monthly spending list. Remove all values less than 100 from monthly_spendings and then print the monthly_spendings list.

### Stuck? Here's a hint!

Create a copy of the list using monthly_spendings[:].