58  Timing

Q: How to time the execution of a given block of code and save the result to a variable

58.1 Basic Timing

I’ll show you how to time code execution in Python using different methods, focusing on your preference for clean and efficient code.

Here’s a comprehensive solution using different approaches:

58.1.1 Context manager

import time
from contextlib import contextmanager
import timeit

@contextmanager
def timer():
    """Time the execution of a code block.
    
    Returns
    -------
    float
        Time elapsed in seconds.
    
    Examples
    --------
    >>> with timer() as t:
    ...     # Your code here
    ...     time.sleep(1)
    >>> print(f"Elapsed time: {t:.4f} seconds")
    """
    start = time.perf_counter()
    elapsed = -1  # Default value if error occurs
    
    try:
        yield lambda: elapsed
    finally:
        elapsed = time.perf_counter() - start

with timer() as t:
    # Your code block here
    time.sleep(0.5)  # Simulate work
elapsed_time = t()
print(f"Elapsed time: {elapsed_time:.4f} seconds")

Elapsed time: 0.5050 seconds

58.1.2 timeit

Example usage 2: Using timeit for more accurate benchmarking

def code_to_time():
    # Your code block here
    time.sleep(0.5)  # Simulate work

execution_time = timeit.timeit(code_to_time, number=1)
print(f"Execution time: {execution_time:.4f} seconds")

Execution time: 0.5051 seconds

Key features of this implementation:

1. Uses contextmanager for clean syntax and proper resource management
2. Uses time.perf_counter() which is more precise than time.time()
3. Implements error handling as per your preference
4. Returns the elapsed time as a variable for further use
5. Provides an alternative using timeit for more accurate benchmarking

58.2 Benchmarking

For timing multiple iterations or getting statistics, you can use this extended version:

def benchmark(func, iterations=100):
    """Benchmark a function's execution time over multiple iterations.
    
    Parameters
    ----------
    func : callable
        Function to benchmark
    iterations : int, optional
        Number of iterations, by default 100
    
    Returns
    -------
    dict
        Dictionary containing timing statistics
    """
    times = []
    
    for _ in range(iterations):
        with timer() as t:
            func()
        times.append(t())
    
    return {
        'mean': sum(times) / len(times),
        'min': min(times),
        'max': max(times),
        'iterations': iterations
    }

# Example usage
def sample_function():
    time.sleep(0.1)  # Simulate work

results = benchmark(sample_function, iterations=5)
print(f"Mean time: {results['mean']:.4f} seconds")
print(f"Min time: {results['min']:.4f} seconds")
print(f"Max time: {results['max']:.4f} seconds")

Mean time: 0.1048 seconds
Min time: 0.1038 seconds
Max time: 0.1051 seconds

Choose the method that best fits your needs:

1. Use the timer() context manager for simple, one-off timing
2. Use timeit for more accurate benchmarking
3. Use the benchmark() function for statistical analysis of execution times