Modules

Reason: Your program gets bigger => need to split it to several files for easier maintenance
A module looks like:

import a module using import command



In [1]:

    
import module_a

print module_a.double(5)









    



Module A is initiating
10

a module is also initialize only once



In [2]:

    
import module_a
import module_b









    



Module B is initiating

using from statement to import name from a module directly



In [3]:

    
from module_b import triple

print triple(5)



In [4]:

    
from module_a import *

print 'single', single(5)
print 'double', double(5)









    



single 5
double 10

import all names will not import those beginning with underscore (_)



In [5]:

    
print _test_func









    



---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-5-3a5f1f17a05c> in <module>()
----> 1 print _test_func

NameError: name '_test_func' is not defined



In [6]:

    
print module_a._test_func









    



<function _test_func at 0x10a119b90>



In [7]:

    
from module_a import _test_func



In [8]:

    
print _test_func









    



<function _test_func at 0x10a119b90>

global variable __name__ contains the module name.



In [9]:

    
print module_a.__name__









    



module_a



In [10]:

    
print __name__









    



__main__

Module search paths

When a module is imported

1. search for a built-in module with that name
2. search in the list of directories given by variable sys.path

sys.path is initialized from:

the directory where python program start, i.e: "current directory"
environment variable PYTHONPATH (syntax like PATH env)
some default locations

Packages

collection of module in the hierarchy structure.
is a folder, which have __init__.py

.
examples/
    mathlib/
        __init__.py
        linalg/
            __init__.py
            dot.py
        not_a_package/
            test.py
        ndarray.py
        random_variable.py



In [11]:

    
import examples









    



---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-11-4f670c18b6bd> in <module>()
----> 1 import examples

ImportError: No module named examples



In [12]:

    
import mathlib









    



---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-12-473487a6008a> in <module>()
----> 1 import mathlib

ImportError: No module named mathlib



In [1]:

    
import sys
sys.path.append('./examples')



In [2]:

    
import mathlib

__init__.py



In [3]:

    
mathlib.random_variable









    



---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-3-5957f58ce91f> in <module>()
----> 1 mathlib.random_variable

AttributeError: 'module' object has no attribute 'random_variable'



In [4]:

    
mathlib.self_introduction()









    



Just a simple math library

import submodule



In [5]:

    
import mathlib.ndarray

print mathlib.ndarray.sum1d([1,2,3])



In [8]:

    
mathlib.ndarray.sum1d









    Out[8]:





<function mathlib.ndarray.sum1d>



In [9]:

    
import mathlib.random_variable as random_variable

print random_variable.draw_uniform(0, 100)



In [10]:

    
s = random_variable



In [11]:

    
s.draw_uniform(0, 100)









    Out[11]:





34



In [12]:

    
from mathlib.linalg import dot

print dot.dot1d([1,2,3], [1,2,3])



In [ ]: