Python Modules

What is a Module?
Consider a module to be the same as a code library.

A file containing a set of functions you want to include in your application.

Create a Module
To create a module just save the code you want in a file with the file extension .py:

Example
Save this code in a file named mymodule.py

def greeting(name):
  print("Hello, " + name)
Use a Module
Now we can use the module we just created, by using the import statement:

Example
Import the module named mymodule, and call the greeting function:

import mymodule

mymodule.greeting("Jonathan")
Note: When using a function from a module, use the syntax: module_name.function_name.

Variables in Module
The module can contain functions, as already described, but also variables of all types (arrays, dictionaries, objects etc):

Example
Save this code in the file mymodule.py

person1 = {
  "name": "John",
  "age": 36,
  "country": "Norway"
}
Example
Import the module named mymodule, and access the person1 dictionary:

import mymodule

a = mymodule.person1["age"]
print(a)
Naming a Module
You can name the module file whatever you like, but it must have the file extension .py

Re-naming a Module
You can create an alias when you import a module, by using the as keyword:

Example
Create an alias for mymodule called mx:

import mymodule as mx

a = mx.person1["age"]
print(a)
Built-in Modules
There are several built-in modules in Python, which you can import whenever you like.

Example
Import and use the platform module:

import platform

x = platform.system()
print(x)
Using the dir() Function
There is a built-in function to list all the function names (or variable names) in a module. The dir() function:

Example
List all the defined names belonging to the platform module:

import platform

x = dir(platform)
print(x)
Note: The dir() function can be used on all modules, also the ones you create yourself.

Import From Module
You can choose to import only parts from a module, by using the from keyword.

Example
The module named mymodule has one function and one dictionary:

def greeting(name):
  print("Hello, " + name)

person1 = {
  "name": "John",
  "age": 36,
  "country": "Norway"
}
Example
Import only the person1 dictionary from the module:

from mymodule import person1

print (person1["age"])
Note: When importing using the from keyword, do not use the module name when referring to elements in the module. Example: person1["age"], not mymodule.person1["age"]