CODEWITHSUNDEEP
pythonmemorymemory-leaks
beCurious
beCurious

Reputation: 152

send custom mail makes memory leaks in python loop?

I think this question is not good for understand, but i have to guess about it.

Status:

I expect, memory usage will be bigger then usual and if i use orm as on, query count will be over then 20,000 count. so i planed this work like this.

  1. get Queryset on database on start. then, make this to dict() with only using data. that dict() call queryset
  2. Every Users has filtered data which name is dataset.

so code will be like this.

for user in every_user:
    filter = user.get_filter()
    dataset = {k: v for k, v in queryset.iteritems() if v['status'] == filter}
    message_html = render_to_string('a.html', dataset)
    send_mail(user.email, message_html)

so, i am worry about dataset and message_html are use memory and, it will make memory leaks (i think..).

so this is question. i have to del dataset and del message_html on that for loop?

Upvotes: 0

Views: 63

Answers (2)

Serge Ballesta
Serge Ballesta

Reputation: 148890

Python uses garbage collection. That means that when a variable has no references on it, it can be freed by the garbage collector. del does not free memory: it just remove the indentifier pointing to the actual variable.

Example:

a = [1,2,3]
b = a
del a

b still points to the list [1,2,3], so it cannot be freed

That means that as dataset and message_html and defined inside the loop they are automatically undefined at the end of each iteration, so del dataset and del message_html is essentially no-op. It just causes an explicit destruction of the identifiers that will be implicitely destroyed on next instruction

TL/DR: in your code del dataset and del message_html on end of loop would be no-op.

For the actual question, in your code, Python will only use memory for one single user and free it before next user iteration.

Upvotes: 2

tanikaze
tanikaze

Reputation: 70

Given the example code, those variables will be garbage collected. There is no need to free them.

If you're nervous, you could simply split the contents of the loop into a function taking the user as a parameter. It is easy to reason that a local variable within a function that is never passed out of the function necessarily is available for garbage collection as soon as the function returns.

Upvotes: 1

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