[Python] What to do when PEP8 is violated in the process of importing from the directory added to sys.path

The version of Python I'm using is 3.6.

If you find any mistakes, I would be grateful if you could point them out in the comments.

Violation of PEP8

Suppose you want to load your own modules under `lib``` from` scripts / execute.py``` with such a directory structure.

.
├──scripts
│   └── execute.py
└──lib
    └── my_module.py

Initially, I tried to deal with it by writing execute.py as follows and adding a file to `` `sys.path```.

import pandas as pd
import sys
sys.path.append('../lib')
import my_module

# (The following is omitted)

However, this is the Python coding convention PEP8 (Japanese translation io / ja / latest / #)) is violated, so if you are using flake8 etc., the following Tsukkomi will be entered.

E402 module level import not at top of file

Let's quote corresponding part of Japanese translation.

The import statement should always be placed at the beginning of the file, immediately after the module comment or docstring, and before the module's global variable or constant definition.

Resolved by setting the environment variable PYTHONPATH

Just I had a question on Stackoverflow to the same effect.

Several methods were answered in this, and adding a directory to the environment variable `` `PYTHONPATH``` seemed to be the essential solution. (The following link was introduced)

• Permanently add a directory to PYTHONPATH

(Although the following methods were also introduced, honestly, it looks like a cunning hack to me.)

• How to prepare a file called pathmagic.py that describes the path reading process and import it
• How to enclose in try ~ except statements

Also, the Japanese question site teratail had answers to similar questions. The answer is from Sphinx committer Shimizukawa, so it seems to be highly credible.

Adjusting sys.path in a script is not recommended. If the directory where you want to use the library is fixed in various places and you want to import that library, there is a way to set the environment variable PYTHONPATH.

So I added the `` `libdirectory to PYTHONPATH and dealt with it. If you use it every time, write it in bash_profile```.

export PYTHONPATH="${PYTHONPATH}:/full path of lib directory/lib"

This allowed us to remove the `` `sys.pathrelated description fromexecute.py```.

import pandas as pd

import my_module

# (The following is omitted)

About the environment variable PYTHONPATH

It's not the main subject, but I was curious about what would happen if the library name and my own module name were batting.

In such cases, read the official documentation. There is the following description in the official Python tutorial.

When importing a module named spam, the interpreter first looks for a built-in module with that name. If not found, look for a file named spam.py in the list of directories in sys.path. sys.path is initialized to the following location:

• The directory containing the entered script (or the current directory if no file is specified).

• PYTHONPATH (list of directory names, same syntax as the shell variable PATH).
• Default per installation.

Apparently, the one in PYTHONPATH has priority. Even when I actually tried it, it behaved like that.