Timer Context Manager

Build a context manager that times code blocks and stores elapsed time.

context-manager timing measurement python

Write a context manager class `Timer` that measures the wall-clock time of a block of code executed inside a `with` statement.

- The class must be initialized with no arguments: `Timer()`.
- When entering the `with` block, record the current time.
- When exiting the `with` block, compute the elapsed time in seconds (float) and store it in the attribute `elapsed`.
- The attribute `elapsed` must be available immediately after the `with` block ends.
- The context manager must suppress no exceptions; it should behave like a normal context manager.
- The object returned by `__enter__` should be the `Timer` instance itself, so that the `with` statement can bind it as a variable.

Implement the class `Timer` with the methods `__enter__` and `__exit__`.

You may use any standard library module (e.g., `time`).

Constraints

The input is not provided; the class is used with a with-block. Elapsed time will be a non-negative float. The test will measure the correctness of storing elapsed time and that the with-block executes normally.

Example

# Example usage:
import time

t = Timer()
with t:
    time.sleep(0.01)

assert t.elapsed >= 0.01

# Another example:
t2 = Timer()
with t2:
    pass
assert t2.elapsed >= 0.0

10 points ~15 min

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Hints

Use time.perf_counter() or time.time() to get the current time before and after the block.

In __enter__, store the start time in an instance attribute, e.g., self.start, and return self.

In __exit__, compute elapsed and assign to self.elapsed.

Remember __exit__ should return None (or False) to not suppress exceptions.

Test Results

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