Is there a logical difference between 'not ==' and '!= (without is)

Question

Is there a substantial difference in Python 3.x between:

for each_line in data_file:
    if each_line.find(\":\") != -1:
        #placeholder for code
               


        

Answer 1

Your first example is how you should be testing the result of find.

Your second example is doing too much. It is additionally performing a boolean not on the result of the each_line.find(":") == -1 expression.

In this context, where you want to use not is when you have something that you can test for truthiness or falsiness.
For example, the empty string '' evaluates to False:

s = ''
if not s:
    print('s is the empty string')

---

You seem to be conflating a little bit the identity-test expressions is and is not with the boolean not.

An example of how you'd perform an identity test:

result_of_comparison = each_line.find(":") == -1
if result_of_comparison is False: # alternatively: is not True
    pass