Describe the flow of execution for except, else, and finally blocks in Python, and explain what happens if the finally keyword is omitted.

Python executes the try block first. If an exception is raised, it searches for an except clause that matches the exception type; when found, it runs that except block. After the except block, or if no exception occurred, Python checks for an else block; the else block runs only when the try block completed without raising an exception. Finally, the finally block runs in all cases, whether an exception was caught or not. The finally block is guaranteed to execute even if the try or except blocks contain return, break, or continue statements. If you omit the finally keyword, any cleanup code that would normally run in finally will not execute, potentially leaving resources open or in an inconsistent state. For example, forgetting to close a file in a finally block can lead to file descriptor leaks. Therefore, finally is essential for ensuring that cleanup actions always occur, regardless of how the preceding blocks exit.