Tracing every executed Python statement#

Today I learned how to use the Python trace module to output every single executed line of Python code in a program - useful for figuring out exactly when a crash or infinite loop happens.

The basic format is to run:

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python3 -m trace --trace myscript.py

This will execute the script and print out every single line of code as it executes - which can be a LOT of output. It slows the program down to a crawl - just starting up Datasette took probably over a minute and churned through hundreds of thousands of lines of console output.

Since Datasette is a command-line application, I needed to use the following recipe to trace it:

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python3 -m trace --trace $(which datasette) fixtures.db -p 8002