Python Essentials

The pass statement as a placeholder

In some algorithms, an else clause may be more important than an if clause. This happens when an algorithm is designed to handle a certain set of conditions—the happy path—by default. All of the other non-happy-path conditions require some exceptional processing.

When the default condition is relatively clear and easy to write, but there's no processing required for the condition, we have a syntax issue in Python. The interesting processing belongs to an else clause, but we have no real code for the initial if clause. Here's a typical pattern shown with invalid syntax:

if happy_path(x):
    # nothing special required
else:
    some_special_processing(x)
# Processing Continues

The happy_path() condition confirms that the ...