'''
In this exercise, you will explore how variables behave when passed to a 
function, and how mutating a list (which is a mutable object) inside a function
affects the original list defined outside the function. You will also observe 
the behavior of immutable objects such as integers and strings when passed to a 
function.
'''

'''
You are given a list of cell counts from different biological samples. 
The function you will implement will add a new value to this list to update it 
with new data. 
Additionally, the function will attempt to modify an integer variable, but 
notice the difference in behavior between the mutable list and the immutable 
integer.

We have a function `update_sample` that:
* Appends a new value to a list of cell counts (this list is defined outside 
the function).
* Attempts to modify a variable (an integer) defined outside the function.

After running this code, observe the behavior of the list and the integer 
variable outside the function.
'''

# Global list (mutable) and integer (immutable) defined outside the function
cell_counts = [100, 120, 130]
total_samples = 3

def update_sample(new_count, cell_counts = cell_counts, total_samples = total_samples):
    # Add new sample count to the list (mutable object)
    cell_counts.append(new_count)
    
    # Attempt to modify total_samples (immutable object)
    total_samples += 1  # This will not affect the global variable!

# Call the function with a new sample count
update_sample(150)

# Print the list and the integer outside the function
print("Updated cell counts:", cell_counts)  # Expected to be updated
print("Total samples:", total_samples)  # Expected to NOT be updated

assert cell_counts == [100, 120, 130, 150], "cell counts should be updated"
assert total_samples == 4, "total samples should be updated"


'''
Why does the list `cell_counts` get updated, but `total_samples` does not change?
Modify the code to fix the behavior of `total_samples` so that it updates correctly. 

Hint: You might need to use the global keyword or return the updated value from 
the function.
'''