Modules

Intermediate Python for Developers

George Boorman

Curriculum Manager, DataCamp

What are modules?

Modules are Python scripts
- Files ending with .py
- Contain functions and attributes
- Can contain other modules
Python comes with several modules
Help us avoid writing code that already exists!

Man looking at reflection, seeing further reflections

Python modules

There are around 200 built-in modules

Popular modules include:
- os - for interpreting and interacting with your operating system
- collections - advanced data structure types and functions
- string - performing string operations
- logging - to log information when testing or running software
- subprocess - to run terminal commands within a Python file

# List all files in a directory
ls

Full list of Python modules: https://docs.python.org/3/py-modindex.html

Importing a module

# General syntax
import <module_name>

# Import the os module
import os

# Check the type
type(os)

<class 'module'>

Finding a module's functions

Look at the documentation

# Call help()
# Warning - will return a very large output!
help(os)

Help on module os:

NAME
    os - OS routines for NT or Posix depending on what system we're on.

MODULE REFERENCE
    https://docs.python.org/3.10/library/os.html

¹ https://docs.python.org/3/library/os.html#module-os

Getting the current working directory

# Using an os function
os.getcwd()

'/home/georgeboorman/intermediate_python_for_developers'

Useful if we need to refer to the directory repeatedly

# Assign to a variable
work_dir = os.getcwd()

Changing directory

# Changing directory
os.chdir("/home/georgeboorman")

# Check the current directory
os.getcwd()

'/home/georgeboorman'

# Confirm work_dir has not changed
work_dir

'/home/georgeboorman/intermediate_python_for_developers'

Module attributes

Attributes have values
Functions perform tasks
Don't use parentheses with attributes

# Get the local environment
os.environ

environ{'PATH': '/usr/local/bin',
        'TERM': 'xterm',
        'HOSTNAME': '097a0fe4-d6ce-4325-a6e2-1d0ce2800c2b',
        'TZ': 'Europe/Brussels',
        'PYTHONWARNINGS': 'ignore',
        'LANG': 'en_US.UTF-8'
        ...}

Importing a single function from a module

Importing a whole module can require a lot of memory
Can import a specific function from a module

# Import a function from a module
from os import chdir

Importing multiple functions from a module

# Import multiple functions from a module
from os import chdir, getcwd


# No need to include os.
getcwd()

'/home/georgeboorman'

Haven't imported os module so Python won't understand

Let's practice!

Intermediate Python for Developers