Python · Const

finally

Python’s finally clause runs cleanup code after a try statement, regardless of whether an exception occurs. It also runs before return, break, or continue leaves the try statement.

How it works

A finally clause is attached to a try statement to run cleanup code after the try block and any applicable except or else clauses. If an exception remains unhandled, it is re-raised after cleanup; control-flow statements in finally can override that behavior.

Syntax

try:
    suite
finally:
    suite

Key points

Use finally for cleanup actions that must run after a try operation.
Execution of finally follows the complete try statement, including its optional except and else parts.
An unhandled exception is retained while the cleanup suite runs.
When cleanup finishes normally, the retained exception is raised again.
The active cleanup suite cannot access the saved exception as ordinary exception information.
Leaving through return, break, or continue still triggers the cleanup suite first.

Common mistakes

Avoid return, break, or continue in finally: these statements discard an exception that would otherwise be re-raised.
A return in finally overrides an earlier return value, so it can silently replace the result from the try block.

Example: Always close a file

def read_config(path):
    file = open(path, encoding="utf-8")
    try:
        return file.read()
    finally:
        file.close()

print(read_config("config.txt"))

The file is closed whether reading succeeds or raises an exception.

When to use it

Release resources

A file, socket, lock, or other external resource must be released after an operation regardless of success or failure.

Restore invariants

Temporary state or bookkeeping must be restored after a protected operation.

Finalize early exits

An operation may exit early through a return or loop-control statement but still needs mandatory finalization.

Interview questions

QWhen does a finally clause run?

finally is a cleanup handler. It runs after the try suite, including any except and else suites, whether or not an exception occurred.

Follow-up: What happens to an unhandled exception? It is temporarily saved, cleanup runs, and the exception is re-raised after the finally suite unless control flow in finally overrides it.

QHow does finally interact with exceptions?

An unhandled exception from the try, except, or else clauses is saved while finally executes. If finally completes normally, that exception is re-raised afterward.

Follow-up: What if finally raises a new exception? The saved exception becomes the context of the new exception.

QWhat happens when control leaves a try statement?

A return, break, or continue in the try suite still causes finally to execute before control leaves. The function's return value is determined by the last return statement executed.

Follow-up: Why is return in finally risky? Because finally always executes, its return is last and can suppress an exception or replace an earlier result.

try statement
except clause
else clause
return statement
break statement
continue statement
with statement

Source: 8. Compound statements. Checked 2026-10-16.