Note_Tech

All technological notes.

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Python - Modules & Package

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• Python - Modules \& Package
  • Module
    • Example
    • Built-in Modules
    • Module Attributes
    • dir() Function
    • Python Built-in Module
    • Run a .py File
    • if __name__ == __main__:
  • Package
    • Pip

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• Cheapsheet: Hierarchy
  • Framework > Library(packages) > Package(directory) > Module(file)

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Module

• module: A document with definitions of functions and various statements written in Python

  • Every python file is a module.
  • A module can define functions, classes, and variables.
  • A module can also include runnable code.
  • A module can be imported from another python file.

• Create a Module

  • Create a module(file) with the file extension .py.

• Syntax

  • Import Module

    • import module_name

  • Re-name Module

    • import module_name as alias

  • Import Function & Variable

    • from module_name import function_name
    • from module_name import variable_name

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Example

• module_person.py

  def greeting(name):
      print("Hello, " + name)
      print(person1)
  
  
  person1 = {
      "name": "John",
      "age": 36,
      "country": "Norway"
  }
  
  

• module_demo.py

  • 1. Import Module

  print("\n--------Import a Module--------\n")
  import module_person
  
  # call the members of the imported module
  module_person.greeting("John")  # function
  person = module_person.person1  # Variables
  print(person)
  # Hello, John
  # {'name': 'John', 'age': 36, 'country': 'Norway'}
  # {'name': 'John', 'age': 36, 'country': 'Norway'}
  

  • 1. Re-name Module

  print("\n--------Re-naming a Module--------\n")
  import module_person as p   # rename imported module
  
  p.greeting("John")
  person = p.person1
  print(person)
  # Hello, John
  # {'name': 'John', 'age': 36, 'country': 'Norway'}
  # {'name': 'John', 'age': 36, 'country': 'Norway'}
  

  • 1. Import Function & Variable

  print("\n--------Import a Function--------\n")
  from module_person import greeting
  
  greeting("John")
  # Hello, John
  # {'name': 'John', 'age': 36, 'country': 'Norway'}
  
  
  print("\n--------Import a Variable--------\n")
  from module_person import person1
  
  person = person1
  print(person)
  
  

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Built-in Modules

import platform

x = platform.system()
print(x)  # Windows

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Module Attributes

• Module Attributes:
  • the attributes to describe module

[print(idf, ":",  eval(idf)) for idf in dir()]
# __annotations__ : {}
# __builtins__ : <module 'builtins' (built-in)>
# __cached__ : None
# __doc__ : None
# __file__ : c:\Users\simon\Documents\IIS\Tech_Notes\Programming_Language\python\trial.py
# __loader__ : <_frozen_importlib_external.SourceFileLoader object at 0x0000028A498E6CD0>
# __name__ : __main__
# __package__ : None
# __spec__ : None

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dir() Function

• dir(): list all the function names (or variable names) in a module.
  • parameter: the name of imported module

import platform

x = dir(platform)
print(x)

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Python Built-in Module

Module	Description
math	math utilities
re	regular expressions
json	JSON
datetime	date and time
sqlite3	use SQLite
os	os utilities
random	random number generation
statistics	statistics generation
requests	perform HTTP network requests
http	to create HTTP servers
urllib	to manage urlsservers

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Run a .py File

• Command Line:

# target file: main.py
python main.py

• Pass arguments from command line

  • py file:
    • imort sys
    • using sys.argv to accept arguments
  • CLI: python file_name.py [arguement]

py Programming_Language\python\lab.py john 16

import sys

print(sys.argv[1:])   # ['john', '16']

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if __name__ == __main__:

• Unlike other languages, Python has no main() function that gets run automatically. The main() function is implicitly all the code at the top level.

• the top-level code is an if block. To identify whether a .py file is original or a imported file:

if __name__ == "__main__":

• __name__ is a built-in variable which evaluate to the name of the current module.
  • If a module is being run directly, then __name__ instead is set to the string "__main__".
  • If a modules function is being used as an import, the __name__ is name of the imported module, not "__main__".

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Package

A module is basically You may choose to define functions, classes, or variables in a module.

• module: a simple Python script with a .py extension file that defines functions, classes, or variables .

• package: a directory of a collection of modules.

  • Packages allow the hierarchical structure of the module namespace.
  • directory also contains an __init__.py file by which the interpreter interprets it as a package.
    • __init__.py Python File works as a Constructor for the Python Package.

• library: a reusable chunk of code.

  • it is often assumed that while a package is a collection of modules, a library is a collection of packages.

• Python frameworks: a collection of modules and packages that help programmers to fast track the development process.

  • However, frameworks are usually more complex than libraries.

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Pip

• pip: The standard package manager for Python

• Download pip: https://pypi.org/project/pip/

• Find pacakge: https://pypi.org/

• import a Package: import <package>

• Pip Commands

Command	Description
pip --version	check the pip version
pip list	List installed packages
pip show <package>	Show information about a package
pip install <package>	downloaded and installed package
pip install <package>==1.0.4	installed specific version
pip install --upgrade <package>	Upgrade package
pip uninstall <package>	Uninstall a package.
pip install -r requirements.txt	Install a list of requirements specified in a file
pip freeze	Generate output suitable for a requirements file
pip freeze > requirements.txt	Generate a txt requirements file

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