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")
Run example »
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)
Run example »
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)
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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
