Modularization

Modules

import math

is used to provide a library

math.sin(3.1415)
# 9.265358966049026e-05

sin(3.1415)
# Traceback (most recent call last):
#   File "<stdin>", line 1, in <module>
# NameError: name 'sin' is not defined

from math import sin, pi

if you import the function directly you don't need to use the "prefix" math. anymore

sin(3.1415)
# 9.265358966049026e-05

however, only the functions that you explicitly import are available,
i.e. sin and pi in our case.

from math import *

You can also import complete libraries, but this could overwrite already existing functions with the same name

pi = 1337
print(pi)
# 1337

from math import *
print(pi)
# 3.141592653589793

Rename

import math as m

you can also simply import the library and assign a new name for the namespace

import math as m
m.pi
# 3.141592653589793

Modul-Types

Python:

• .py
• .pyc

C-Modules:

• .pyd
• .dll
• .so
• …

c modules linked with the interpreter:

import sys
print(sys.builtin_module_names)
# …

Search For Modules

when importing a module, the interpreter searches in the following directories:

1. in the current directory
2. pythonpath
3. if pythonpath is not set the default directory is searched for

with sys.path you get the directories you are searching in

Contents

with the help of the function "dir" you get all names defined in a module

import math
dir(math)
# …

without an argument "dir" returns all names defined in the namespace

import math
blibla = 123
bli = "asldfhioasp9dasdapsdas"
dir()
# …

Own Modules

creating your own python module is extremely easy since every python file is automatically a module

must be present in the search path (Search For Modules)

import example_py_file

Documetation

we can use docstring's to document our modules

help(example_py_file)

Docstring

Packages

like creating a module in python, creating a package is just as easy

create a folder with the following struct:

the file __init__.py can be empty

the modules can now be imported with:

from simple_package import a, b

import simple_package

will generate an error message because the modules must be imported individually

to change this we can put: from simple_package import a, b in __init__.py