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.pydef 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”)
Output:
C:\Users\My Name>python demo_module1.py
Hello, 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)
Output:
C:\Users\My Name>python demo_module2.py
36
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)
Output:
C:\Users\My Name>python demo_module3.py
36
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)
Output:
Windows
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)
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’]
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”])
Output:
C:\Users\My Name>python demo_module6.py
36
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"]