Modules and packages in python

Modules and Packages
in Python
Dr.T.Maragatham
Kongu Engineering College, Perundurai

Modules
• Modules - a module is a piece of software
that has a specific functionality. Each module
is a different file, which can be edited
separately.
• Modules provide a means of collecting sets of
Functions together so that they can be used
by any number of programs.
Dr.T.Maragatham Kongu Engineering
College, Perundurai

Packages
• Packages – sets of modules that are grouped
together, usually because their modules
provide related functionality or because they
depend on each other.
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Modules
• programs are designed to be run, whereas
modules are designed to be imported and
used by programs.
• Several syntaxes can be used when importing.
For example:
• import importable
• import importable1, importable2, ...,
importableN
• import importable as preferred_name
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• make the imported objects (variables, functions,
data types, or modules) directly accessible.
• from …import syntax to import lots of objects.
• Here are some other import syntaxes:
• from importable import object as preferred_name
• from importable import object1, object2, ...,
objectN
• from importable import (object1, object2,
object3, object4, object5, object6, ..., objectN)
• from importable import *
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Python import statement
• We can import a module using
the import statement and access the
definitions inside it using the dot operator.
• import math
• print("The value of pi is", math.pi)
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Import with renaming
• We can import a module by renaming it as
follows:
• # import module by renaming it
• import math as m
• print("The value of pi is", m.pi)
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Python from...import statement
• We can import specific names from a module
without importing the module as a whole.
Here is an example.
• # import only pi from math module
• from math import pi
• print("The value of pi is", pi)
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Import all names
• We can import all names(definitions) from a
module using the following construct:
• from math import *
• print("The value of pi is", pi)
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The dir() built-in function
• We can use the dir() function to find out names that
are defined inside a module.
• we have defined a function add() in the
module example that we had in the beginning.
• dir(example)
• ['__builtins__', '__cached__', '__doc__', '__file__',
'__initializing__', '__loader__', '__name__',
'__package__', 'add']
• a sorted list of names (along with add).
• All other names that begin with an underscore are
default Python attributes associated with the module
(not-user-defined).
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Let us create a module
• Type the following and save it as example.py.
• # Python Module example
• def add(a, b):
– """This program adds two numbers and return the
result"""
– result = a + b
– return result
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How to import modules in Python?
import example
example.add(4,5.5)
9.5 # Answer
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Variables in Module
• The module can contain functions, as already
described, but also variables of all types
(arrays, dictionaries, objects etc):
• Save this code in the file mymodule.py
• person1 = {
"name": "John",
"age": 36,
"country": "Norway"
}
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• Import the module named mymodule, and
access the person1 dictionary:
• import mymodule
a = mymodule.person1["age"]
print(a)
• Run Example  36
•
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Built-in Modules
• Import and use the platform module:
• import platform
x = platform.system()
print(x)
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Import From Module
• 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"])
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• def greeting(name):
print("Hello, " + name)
person1 = {
"name": "John",
"age": 36,
"country": "Norway"
}
• Example
• Import all objecs from the module:
• from mymodule import *
print(greeting(“Hello”)
print (person1["age"])
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What are packages?
• We don't usually store all of our files on our
computer in the same location.
• We use a well-organized hierarchy of
directories for easier access.
• Similar files are kept in the same directory, for
example, we may keep all the songs in the
"music" directory.
• similar to this, Python has packages for
directories and modules for files
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• As our application program grows larger in
size with a lot of modules, we place similar
modules in one package and different
modules in different packages.
• This makes a project (program) easy to
manage and conceptually clear.
• Similarly, as a directory can contain
subdirectories and files, a Python package
can have sub-packages and modules.
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A Simple Example
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• First of all, we need a directory. The name of this
directory will be the name of the package, which
we want to create.
• We will call our package "simple_package". This
directory needs to contain a file with the
name __init__.py.
• This file can be empty, or it can contain valid
Python code.
• This code will be executed when a package is
imported, so it can be used to initialize a
package.
• We create two simple files a.py and b.py just for
the sake of filling the package with modules
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__init__.py
• A directory must contain a file
named __init__.py in order for Python to
consider it as a package.
• This file can be left empty but we generally
place the initialization code for that package in
this file
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My Documents
My_Package
__init__.py First.py Second.py
Package
Main.py
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• First.py
def one():
print(“First Module”)
return
• Second.py
def second():
print(“Second Module”)
return
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Main.py
• from My-Package import First
• First.one()
• from My-Package import First,Second
• First.one()
• Second.second()
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• For example, if we want to import
the start module in the above example, it can
be done as follows:
• import Game.Level.start
• Now, if this module contains
a function named select_difficulty(), we must
use the full name to reference it.
• Game.Level.start.select_difficulty(2)
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• If this construct seems lengthy, we can import
the module without the package prefix as
follows:
• from Game.Level import start
• We can now call the function simply as
follows:
• start.select_difficulty(2)
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• Another way of importing just the required
function (or class or variable) from a module
within a package would be as follows:
• from Game.Level.start import select_difficulty
Now we can directly call this function.
• select_difficulty(2)
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