Module and Importing in Python

 

Module and Importing

• Every single .py file or a python script file is a separate module in python.
• Suppose if your application have 2 .py(python script) file, then you application have 2 modules.
• to use one module (identifiers from one module) to other, we need to import the module to other.
• Importing is done with the keyword import

Syntax:

        keyword_import _module name

to use identifiers / variables from imported module, we use module_name

module_name.variable.identifier_name

with import we can import

• full module
• single/multiple function
• single/multiple Class object
• combination of function variable and class object.

let's we have a module file1.py as below

 #program in file1.py
 a=10
 b=20
 def add():
     return a+b;

now we are in need to import file1.py in file2.py 

Few ways of importing a module and how to get access to its content(variable/function) 

case 1: import module

• here we are importing module 

• we need to use module name to access content(variable/function) in module file1.py

 #program in file2.py

 import file1
 print("a :",file1.a)
 print("b :",file1.b)
 result = file1.add()
 print("sum is : ",result)

Output will be

 a : 10
 b : 20
 sum is :  30

case 2: import module as alias

• here we are importing module file1 as f1(alias)

• we can access files 1 content(variable/function) with this alias name

 #program in file2.py

 import file1 as f1
 print("a :",f1.a)
 print("b :",f1.b)
 result = f1.add()
 print("sum is : ",result)

Output will be

 a : 10
 b : 20
 sum is :  30

case 3: from module import all

•  to import all data we use *(star)

• directly we can access file 1 content(variable/function) without imported module name reference

 #program in file2.py

 from file1 import *
 print("a :",a)
 print("b :",b)
 result = add()
 print("sum is : ",result)

Output will be

 a : 10
 b : 20
 sum is :  30

case 4: from module import specific(variable/function/class object) 

• we are importing only variable a and b

• we can directly call content(variable/function) of module file1.py by name

 #program in file2.py

 from file1 import a,b
 print("a :",a)
 print("b :",b)
 result = add()
 print("sum is : ",result)

output will be

 a : 10
 b : 20
 Traceback (most recent call last):
   File "C:\Self_Practice_Er_M_S_Dandyan\Python\file2.py", line 6, in <module>
     result = add()
 NameError: name 'add' is not defined

As we have not imported function add() from file.1, so we cannot use it in file2.py