A module is a code library, within an external file, containing a set of functions that can be included in a Python application.

To create a module, specified code is saved in a file with the file extension .py.

The following can be saved into a file called myModule.py.

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

The import statement, using the following syntax, is used to call the myModule.py file.

Syntax:

module_name.function_name

Importing and Using:

import myModule
myModule.greeting("Johnny")

Output:

Hello, Johnny

A module can contain variables of all types (arrays, dictionaries, objects, etc.).

The following imports the module “myModule” and accesses the person dictionary.

import myModule

x = myModule.person["age"]
print(x)

Output:

12

An alias can be created when you import a module by using the as keyword.

import myModule as mm

x = mm.person["age"]
print(x)

Output:

12

There are numerous built-in modules in Python, that can be imported and used. For example, the platform module is a built-in module that contains the dir() function which lists all the function or variable names contained in ANY module, whether built-in or created.

import platform

x = dir(platform)
print(x)

Output:

['DEV_NULL', '_UNIXCONFDIR', 'WIN32_CLIENT_RELEASES', 'WIN32_SERVER_RELEASES', '__builtins__', '__cached__', '__copyright__', '__doc__', '__file__', '__loader__', '__name__', '__package __', '__spec__', '__version__', '_default_architecture', '_dist_try_harder', '_follow_symlinks', '_ironpython26_sys_version_parser', '_ironpython_sys_version_parser', '_java_getprop', '_libc_search', '_linux_distribution', '_lsb_release_version', '_mac_ver_xml', '_node', '_norm_version', '_perse_release_file', '_platform', '_platform_cache', '_pypy_sys_version_parser', '_release_filename', '_release_version', '_supported_dists', '_sys_version', '_sys_version_cache', '_sys_version_parser', '_syscmd_file', '_syscmd_uname', '_syscmd_ver', '_uname_cache', '_ver_output', 'architecture', 'collections', 'dist', 'java_ver', 'libc_ver', 'linux_distribution', 'mac_ver', 'machine', 'node', 'os', 'platform', 'popen', 'processor', 'python_branch', 'python_build', 'python_compiler', 'python_implementation', 'python_revision', 'python_version', 'python_version_tuple', 're', 'release', 'subprocess', 'sys', 'system', 'system_aliases', 'uname', 'uname_result', 'version', 'warnings', 'win32_ver']

To import only parts from a module, use the from keyword.

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

person1 = {
    "name": "Johnny",
    "age": 12
}
person2 = {
    "name": "Marty",
    "age": 57
}

from myModule import person1
print(person["age"])

Output:

12

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