Explain the difference between sets and lists in Python.
Certainly! In Python, both sets and lists are used to store collections of items, but they differ in several important ways.

A list is an ordered collection of items that can be indexed and modified. You can add or remove items from a list using various methods like .append(), .insert(), .remove(), and others. Lists are denoted by square brackets [].

On the other hand, a set is an unordered collection of unique items that cannot be indexed or modified. You can add or remove items from a set using methods like .add(), .discard(), and others. Sets are denoted by curly braces {}.

Here's an example to illustrate the difference:
```python
my_list = [1, 2, 3, 3, 4, 5]  # this list can contain duplicate values
my_set = {1, 2, 3, 3, 4, 5}  # this set contains only unique values

print(my_list)  # output: [1, 2, 3, 3, 4, 5]
print(my_set)   # output: {1, 2, 3, 4, 5}
```
In summary, lists are ordered and allow duplicates, while sets are unordered and contain only unique values.
Please write a python script that can take a list or a set as an input, and that returns a set if it is a list, and a list if it is a set. Use a fonction named invert_sl.
Sure, here's an implementation of the invert_sl function that takes a list or a set as an input and returns a set if it is a list and a list if it is a set:

```python
def invert_sl(input):
    if isinstance(input, list):
        return set(input)
    elif isinstance(input, set):
        return list(input)
    else:
        raise TypeError(Input must be a list or a set)
```

Here's how you can use this function:

```python
my_list = [1, 2, 3, 3, 4, 5]
my_set = {1, 2, 3, 4, 5}

# Convert list to set
new_set = invert_sl(my_list)
print(new_set)  # output: {1, 2, 3, 4, 5}

# Convert set to list
new_list = invert_sl(my_set)
print(new_list)  # output: [1, 2, 3, 4, 5]
```

The function first checks if the input is a list or a set using the isinstance() function. If the input is a list, it returns a set using the set() function. If the input is a set, it returns a list using the list() function. If the input is neither a list nor a set, it raises a TypeError.
How could I do it without using those standard library functions? e.g. isinstance(), etc