Python / Import module within a defined function?

Question

would you recommend using the import outside of the function or within is fine?

Any recommendations/critics welcome. Thanks

import time
import datetime

# Time Since 
def time_since(since):
    now = datetime.now()
    unixtime = calendar.timegm(now.utctimetuple())
    since = unixtime - 60 * 60 * 24 * 20


# Execute code every 60 sec 
def autorun(seconds):
    import time
    starttime = time.time()
    while True:
    print("tick")
    time.sleep(seconds - ((time.time() - starttime) % seconds))

If you have it within a function it will import every time you call the function, which is why it is not recommended. — Albin Sidås, Aug 05 '22 at 10:23

score 1 · Answer 1 · answered Aug 05 '22 at 10:26

1

Imports should be at the top of the file unless you have a circular dependency. In that case, to fix it we have to import it within the function where we want to use it.

To read more about circular import go through this.

answered Aug 05 '22 at 10:26

Tasawer Nawaz

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score 1 · Accepted Answer · answered Aug 05 '22 at 10:34

For this use case just import once at the start of the file; it's not going to change the performance by any tangible amount.

One reason to include the import statement within the function is to lazy load the import, i.e., the module is only loaded when the function is called and not on start up of the module.

This can be beneficial for some use cases, we can see this in the Python source code of the Counter module within collections package: Counter source code

heapq is lazy loaded to speedup Python startup time

Also see this discussion on how Python deals with attempts to import a module multiple times: https://stackoverflow.com/a/37077911/15981783.
tl;dr it doesn't, if module is imported python just gets module object.

Python / Import module within a defined function?

2 Answers2