All 15 Debugging & Profiling questions
More in Debugging & Profiling
How do you use the built-in pdb debugger to pause execution at a specific line? How do you use print statements effectively for debugging, including showing variable names alongside values? How do you use the traceback module to capture and format a full exception traceback as a string, useful for logging? How do you use the timeit module to accurately measure a small code snippet's execution time? How do assert statements work for debugging, and why should they NOT be relied upon for production input validation? How do you use Python's built-in 'warnings' module to surface deprecated or risky code paths during debugging? How would you use the 'faulthandler' module to diagnose a program that crashes with a segmentation fault, typically from a C extension? How do you use memory_profiler (or tracemalloc from the standard library) to identify a memory leak's source in a Python application? How would you use the 'logging' module's exception logging (logger.exception()) INSIDE an except block to automatically capture the full traceback? How do you use pdb's post-mortem debugging mode to inspect a program's state exactly at the point where an unhandled exception occurred?
Advertisement
Back to results for “Debugging & Profiling”
Python › Debugging & Profiling

How do you use cProfile to identify which functions are consuming the most time in a larger program?

Intermediate

Answer

Run your program (or a specific function call) through cProfile.run() or the command line (`python -m cProfile script.py`), which produces a detailed report showing call counts, cumulative time, and per-call time for every function invoked — pinpointing exactly where performance bottlenecks actually are, rather than guessing.
import cProfile

def slow_function():
    return sum(i * i for i in range(1_000_000))

cProfile.run("slow_function()")
# Prints a table: ncalls, tottime, percall, cumtime, percall, filename:lineno(function)
Real-world example Identifying the actual performance bottleneck in a slow script before deciding what to optimize, rather than guessing.

Common follow-ups: What does the 'cumtime' column specifically measure, versus 'tottime', in cProfile's output?

Debugging & Profiling
All 15 Debugging & Profiling questions