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")
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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)
Run Example »
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)
Run Example »
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)
Try it Yourself »
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)
Try it Yourself »
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"])
Run Example »
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"]
Where to Store a Module?
You can store the modules in the same directory as the rest of your python files, or you can choose a different location.
Python will start by searching the current directory, then it will search in every location described in the PYTHONPATH variable.
To see which locations that are described in the PYTHONPATH variable, check the sys.path property:
Example
List all the locations described in the PYTHONPATH property:
import sys
print(sys.path)
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To add locations to the PYTHONPATH variable use the set PYTHONPATH statement:
Example
Add a new location to the PYTHONPATH property:
C:\Users\Your Name>set PYTHONPATH = C:\Users\Your Name\python_modules
Try it Yourself »
Note: The dir() function can be used on all modules.
