Sharing functions and variables across files in python

on
using_variables_functions_across_files

Skill - Sharing functions and variables across files in python

Table of Contents

Skills Required

Please make sure to have all the skills mentioned above to understand and execute the code mentioned below. Go through the above skills if necessary for reference or revision

Sharing variables and functions defined in one file with other files can be very useful to

  • reduce the size and duplication of the application code by defining variables and function only in one file
  • increase the readability and maintainability of the application code, since we can split the code across different files and folders
  • implement coding practices like separation of concerns, single responsibility principle etc.,

Folder structure for this example

sharing_variables_demo_file_structure

  • Entry file for executing this application is index.py
  • The code of our example python application will be distributed across the folders as shown in the above image
  • Notice that each folder has __init__.py file inside it. This is required for sharing the code inside the folder.
    Hence ensure each folder has __init__.py file inside it

Code in each file

# stores/persons_store.py
persons = [
    {'name': 'Sudhir', 'age': '28'},
    {'name': 'Lakshmi', 'age': '27'},
    {'name': 'Aditya', 'age': '27'},
    {'name': 'Kishore', 'age': '24'},
]

# utils/info_creator.py
def createInfoForPerson(p):
    return 'Name - {0}, Age - {1}'.format(p['name'], p['age'])

# utils/get_all_persons_Info.py
from stores.persons_store import persons
from utils.info_creator import createInfoForPerson

def getAllPersonsInfo():
    infoArray = []
    for p in persons:
        personInfo = createInfoForPerson(p)
        infoArray.append(personInfo)
    return infoArray

# index.py
from utils.get_all_persons_Info import getAllPersonsInfo

personsInfoList = getAllPersonsInfo()

print('All persons in the store are ...')
print('\n'.join(personsInfoList))

File paths in the ‘from’ statement while importing

  • In get_all_persons_Info.py file statement used to import the function createInfoForPerson was
from utils.info_creator import createInfoForPerson
  • Even though info_creator.py file is in the same folder as that of get_all_persons_Info.py, we used utils.info_creator
  • this is because, the file-path during import should be based on the entry python file. In our case the entry file was index.py and hence the import path is with respect to index.py as utils.info_creator

Executing the example application code

  • The code should be executed by running index.py
  • If we run other files in the folders, we will get errors at the import statements because the imports are all defined relative to the folder level of index.py
  • Hence all the code that is to be executed needs to be in the same folder as that of entry file (index.py) in order to avoid import errors. This is a constraint to be considered in the application code design in order to use shared variables and functions concept

Points to remember

  • file-paths used in the import statements are to be written relative to the entry python file, not as per the python file in which the import statement
    Many people get confused with this concept
  • ensure __init__.py file is in all folders in which the variables of python files are to be shared

Video

The video tutorial for this post can be found here

References

Table of Contents

Comments

Post a Comment