Question

In Python, if I have a child function within a parent function, is the child function "initialised" (created) every time the parent function is called? Is there any performance overhead associated with nesting a function within another?

Answer 1

Yes, a new object would be created each time. It’s likely not an issue unless you have it in a tight loop. Profiling will tell you if it’s a problem.

In [80]: def foo():
   ....:     def bar():
   ....:         pass
   ....:     return bar
   ....: 

In [81]: id(foo())
Out[81]: 29654024

In [82]: id(foo())
Out[82]: 29651384