Picking the threshold value for list elements in Python

I have a list Cb. If any element of Cb is greater than threshold_Cb, I want to be that element equal to threshold_Cb. But I am getting error. I present the expected output.

Cb=[[0.001,
  7.557543577091797e-06,
  1656.90]]

threshold_Cb=10.0

if Cb > threshold_Cb:
    Cb = threshold_Cb
    print(Cb)

The error is

in <module>
    if Cb > threshold_Cb:

TypeError: '>' not supported between instances of 'list' and 'float'

The expected output is

Cb=[[0.001,
  7.557543577091797e-06,
  10.0]]

You can use:

new_Cb = [[x if x <= threshold_Cb else threshold_Cb for x in Cb[0]]]

Comprehensions like the above are more efficient than loops. Cb[0] is required because you have a nested List and the [[ ...]] in the above is because you want a nested List.

gives

[[0.001, 7.557543577091797e-06, 10.0]]

You have a nested list (aka a list inside a list). When you run your code, it is iterating over the outer list (Cb). This means that will try to compare

[0.001,
7.557543577091797e-06,
1656.90] with your threshold (threshold_Cb=10.0), and this is the source of your error.
What you need is to iterate over elements in [0.001, 7.557543577091797e-06, 1656.90] and compare them to threshold_Cb.

1) Solution:

   Cb=[[0.001,
      7.557543577091797e-06,
      1656.90]]
    
    threshold_Cb=10.0
    
    for inner_list in Cb:
        for index, element in enumerate(inner_list): 
            if element > threshold_Cb:
                inner_list[index] = threshold_Cb
    
    
    print(Cb)
[[0.001, 7.557543577091797e-06, 10.0]]

You need to iterate over every item in the nested list and compare them individually:

Cb=[[0.001,
  7.557543577091797e-06,
  1656.90]]

threshold_Cb=10.0
# Iterating over the first list within the nested list you have
for index, value  in enumerate(Cb[0]):
    # checking if the value is above treshold
    if value > threshold_Cb:
        # Reassigning the value with index
        Cb[0][index] = threshold_Cb
print(Cb)

Output:

[[0.001, 7.557543577091797e-06, 10.0]]

Otherwise your "if" statement is comparing if a nested list is larger than an integer and that is not a meaningful comparison. Hence your error message.

When Cb has more than one lists inside it you can do this:

# iterating over nested lists inside Cb
for lst_index, lst in enumerate(Cb):
    # Iterating over the nested list values
    for value_index, value  in enumerate(lst):
        # checking if the value is above treshold
        if value > threshold_Cb:
            # Reassigning the value with index
            Cb[lst_index][value_index] = threshold_Cb

If you want to modify Cb in situ rather than create a new list I suggest:

Cb = [
    [
        0.001,
        7.557543577091797e-06,
        1656.90
    ]
]

threshold_Cb = 10.0

for e in Cb:
    e[:] = [min(v, threshold_Cb) for v in e]

print(Cb)

Output:

[[0.001, 7.557543577091797e-06, 10.0]]

Note:

Concise code (such as this) isn't necessarily most efficient and this is certainly one of those cases