How to use Profilers in Python

When you have performance problems in your Python application, you can use a Profiler to help you.

Step 1: Using cProfile

Your first option is to run your application with -m cProfile in the cli.

Let’s take an example application that is run as follows:

python app.py

We can run it with a Profiler by doing the following:

python -m cProfile -o outfile app.py

This will give you a report that shows where most of the time is spent while running your app.

Step 2: Using LineProfiler (recommended)

My preferred option, is to use the line_profiler tool to perform a more detailed scan.

Start by installing the line_profiler using pip.

pip install line_profiler

Then we can adjust our application code and add the @profile annotation right before each function you’d like to see statistics with.

@profile
def fun_a():
    #do something

@profile
def fun_b():
    #do something more

if __name__ == '__main__':
    fun_a()
    fun_b()

Now we can run the profiler using the below command:

time kernprof -l -v app.py