If we create our custom module and there are somt lines that must not be executed during imports in another py file we should put this code in:

if __name__ == "__main__":
    print("some code")

Name of python file that you DIRECTLY execute is __main__

Good imports styling:

"""
Illustration of good import statement styling.

Note that the imports come after the docstring.
"""

# Standard library imports
import datetime
import os

# Third-party imports
from flask import Flask
from flask_restful import Api
from flask_sqlalchemy import SQLAlchemy

# Local application imports
from mod1 import Foo
from mod2 import Bar

Naming guard if __name__ == "__main__" :

# Suppose this is foo.py.

print("before import")
import math

print("before function_a")
def function_a():
    print("Function A")

print("before function_b")
def function_b():
    print("Function B {}".format(math.sqrt(100)))

print("before __name__ guard")
if __name__ == '__main__':
    function_a()
    function_b()
print("after __name__ guard")

import #module #hiding

import math, sys

pi = 32342
print(pi)
print(math.pi)

importing-that-affects-namespace #hiding

from math import sin, pi

print(sin(pi / 2))


pi = 3.14
def sin(x):
    if 2 * x == pi:
        return 0.99999999
    else:
        return None


print(sin(pi / 2))

aggressive import (everything)

from math import *

alias

import math as m

print(m.sin(m.pi/2))

from math import pi as PI, sin as sinus
print(sinus(PI/2))