Profile Python import times

Question

Is there a way to find out which imports are taking the longest in Python? Looking at the output of python -m cProfile <script>, it doesn't seem to include import statements (understandably given potentially huge dependency trees). Initially I thought it did since I saw a row for __import__() calls, but I think this might actually be because code somewhere is explicitly calling it, toy programs with only import statements don't have a row for it.

Right now I'm just using:

start = time.time()
import <module>
print '%s / time: %f' % (<module>, time.time()-start)

around each module, but it doesn't profile it recursively to see which import within an import might be inflating the time.

Answer 1

This is a totally legitimate question. For instance, it makes sense to try to accelerate cold start for CLI applications. Python 3.7 now offers an option to print the import time: https://docs.python.org/3/using/cmdline.html#envvar-PYTHONPROFILEIMPORTTIME

You can either run:

python -X importtime myscript.py

or:

PYTHONPROFILEIMPORTTIME=1 myscript.py

EDIT: to view those results I recommend tuna.