TypeError: 'list' object is not callable while trying to access a list?

I am trying to run this code where I have a list of lists. I need to add to inner lists, but I get the error TypeE...

The difference between the Runnable and Callable interfaces in Java?

What is the difference between using the Runnable and Callable interfaces when designing a concurrent thread in Java...

What is a “callable”??

Now that it's clear what a metaclass is, there is an associated concept that I use all the time without knowing what...