Importing modules in Python - best practice

Question

I am new to Python as I want to expand skills that I learned using R. In R I tend to load a bunch of libraries, sometimes resulting in function name conflicts.

What

Answer 1

Here are some recommendations from PEP8 Style Guide.

1. Imports should usually be on separate lines, e.g.:

   Yes: import os
        import sys
   
   No:  import sys, os
   

   but it is okay to

   from subprocess import Popen, PIPE
   

2. Imports are always put at the top of the file, just after any module comments and docstrings, and before module globals and constants.
   

   • Imports should be grouped in the following order:
     1. standard library imports
     2. related third party imports
     3. local application/library specific imports
   • You should put a blank line between each group of imports.

3. Absolute imports are recommended
   They are more readable and make debugging easier by giving better error messages in case you mess up import system.

   import mypkg.sibling
   from mypkg import sibling
   from mypkg.sibling import example
   

   or explicit relative imports

   from . import sibling
   from .sibling import example
   

4. Implicit relative imports should never be used and is removed in Python 3.

   No:  from ..grand_parent_package import uncle_package
   

5. Wildcard imports ( from import * ) should be avoided, as they make it unclear which names are present in the namespace, confusing both readers and many automated tools.

---

Some recommendations about lazy imports from python speed performance tips.

Import Statement Overhead

import statements can be executed just about anywhere. It's often useful to place them inside functions to restrict their visibility and/or reduce initial startup time. Although Python's interpreter is optimized to not import the same module multiple times, repeatedly executing an import statement can seriously affect performance in some circumstances.

the given below is a scenario explained at the page,

>>> def doit1():
... import string
... string.lower('Python')
...
>>> import string
>>> def doit2():
... string.lower('Python')
...
>>> import timeit
>>> t = timeit.Timer(setup='from __main__ import doit1', stmt='doit1()')
>>> t.timeit()
11.479144930839539
>>> t = timeit.Timer(setup='from __main__ import doit2', stmt='doit2()')
>>> t.timeit()
4.6661689281463623