Modules and Packages in Python | Manohar Papasani

Modules
-------
A module is collection of variables,functions and classes.
The program itself in python is a module.
The file name is the module name with the suffix .py appended
Definitions from a module can be imported into other modules or into the main module.
module is reusable.
module provides readability.
modules avoids naming collisions.

Modules typically define a separate namespace, which helps avoid collisions between identifiers in different areas of a program.

Functions, modules and packages promote code modularization.

Note:
save a module in Lib folder inside installtion folder so that we have access to the modules from anywhere in our local machine.

test123.py
a=10

def f1():
print("abc")

def f2():
print("bbc")

save as in

ex 2)
import test123
test123.a
10
test123.f1()
abc
test123.f2()
bbc

The import statement
syntax
------
import module1,module2,......

ex1:
import math,os,sys

ex2:
import module

How access members of a module
------------------------------
syntax
------
modulename.varname
or
modulename.function_name(parameterlist)
or
modulename.classname

ex:
module.f1()
module.f2(10,20)

ex 8)

a=10
b=20

def f1():
print("hi")

def f2(a,b):
print("hi",a,b)

def f3(a,b,c):
print("hi",a,b,c)

def f4(a,b,c,d):
print("hi",a,b,c,d)

def f5(a,b,c,d,e):
print("hi",a,b,c,d,e)

class Foo:
pass

save modules.py


The from import Statement

An alternate form of the import statement allows individual objects from the module to be imported directly into the caller’s symbol table:

import .. has the following syntax :

from module_name import name(s)

Following execution of the above statement, name(s) can be referenced in the caller’s environment without the module_name prefix:

ex 9)

from modules import f1,f2

f1()
f2(10,20)
f3(1,2,3)
f4(1,2,3,4)
f5(1,2,3,4,50

ex 10)

from modules import Foo

x=Foo()
x

module.Foo object at 0x02E3AD50

Because of form .. import.. ,the object names directly placed into the caller’s symbol table, any objects that already exist with the same name will be overwritten:

ex 11)

a=100
a
100
from modules import a
a
10


ex12)

def tri(b,h):
return 1/2*b*h

def rec(l,b):
return 1/2*b*h

def circle(r):
return 3.14*r*r

save as shapes.py

Python Importing Multiple Modules Example
Several comma-separated modules may be specified in a single import statement:

import modulename1,modulename2,......


ex 13)

import shapes,modules

print(shapes.tri(10.0,20.0))
module.f1()


You can import whole of the module using

syntax
------
from module_name import *

ex 14)
from modules import *

f1()
f2(10,20)

Note:
This isn’t necessarily recommended in large-scale production code. It’s a bit dangerous because you are entering names into the local symbol table en masse.


ex 15)
from module,shapes import *

f1()
f2(10,20)
tri(10,20)