What is a "line marker" icon in PyCharm?

Question

What is this "line marker" icon in the gutter in PyCharm IDE? When does it appear exactly?

I looked up but this doesn't explain much about the icon itself.

Answer 1

The "Line Marker" (or green run icon) in the gutter is added by PyCharm to special lines the IDE considers as runnable. This is not only the case for lines containing a Top level script enviorment but also frequent with executable test functions from testing frameworks, for example with pytest among others.

The PyCharm IDE detects these automatically (for example by prefixing a function name with test and having a testing framework configurered). One good example of this is the following thread where the IDE makes a mistake detecting a line as runnable, see PyCharm: FooTestCase is no test, but FooTest is.

Answer 2

It represents the entry point into the application - the line that is first invoked when you run the code.

You have some options when you click on it to run the code in a number of ways, for example with profiling or debugging.