Python Advanced--02 How to use the module

1. Concept of module and package 1.1

Module: After a lot of code, it is not easy to maintain in a. py file, splitting the code into multiple. py files, each of which is a module.

Package: After more modules, it is also easy to duplicate the name, each development module can be put into different packages, referring to the use of package names. Module name.

1.2 Advantages

Variables of the same variable name do not affect each other in different modules

Modules with the same module name do not affect each other in different packages

1.3 Reference Examples

# p1-> Package name,util-> module name

>>> Import P1.util

>>> print P1.UTIL.F (2,10)

1.4 How to differentiate between packages and normal folders

In a file system, a package is a folder;

In Python, each package must have a __init__.py file below it;

__init__.py file Even if it is empty, there should be.

2. Import of Modules 2.1 Direct import

Import Math

>>> Math.pow (2, 0.5) # POW is a function

1.4142135623730951

>>> Math.PI # pi is a variable

3.141592653589793

2.2 Using from ... import xxx

From math import pow, sin, log

>>> Pow (2, ten)

1024.0

>>> sin (3.14)

0.0015926529164868282

2.3 Method/variable conflict issues in imported modules

Direct import will not have a conflict problem

Use the From ... import xxx If there is a conflict, you can use the alias way

From Math import log

The log of from logging import log as Logger # logging now becomes logger

Print log (10) # is called the log of math

Logger (' Import from Logging ') # called the Log of logging

3. Dynamic Import Module 3.1 background

If the imported module does not exist, the Python interpreter will report a importerror error;

In some cases, two different modules provide the same functionality

3.2 principle

Using Importerror error, we can implement dynamic import module through exception handling try-except.

Another,import xxx as XXX can dynamically import modules of the same name for different use names

3.3 Examples

Try

From Cstringio import Stringio

Except Importerror:

From Stringio import Stringio

Or

Try

Import Simplejson as JSON

Except Importerror:

Import JSON

4.__FUTURE__ trial new features 4.1 background

New versions of Python introduce new features, but in fact these features already exist in the previous version. To "try out" a new feature, you can do so by importing some of the features of the __future__ module.

4.2 Examples

# Python 2.7 Integer division result is an integer, Python 3.x has improved the division of integers, "/" In addition to get floating point number, "//" is still an integer

>>> Print 10/3

3

>>> from __future__ Import Division

>>> Print 10/3

3.33333333333

# in Python 3.x, string unification is Unicode, no prefix u is required, and str stored in bytes must prefix b

>>> from __future__ import unicode_literals

>>> s = ' am I an Unicode? '

>>> Print isinstance (S, Unicode)

True

5. Install the third-party module 5.1easy_install5.2 python built-in Pip (already built into 2.7.9)

Select Pip function When installing

Once the installation is complete, you can install web.py this third-party module by using PIP install web.py on the command line

When the third-party module is installed, use the import Web to work properly

Third-party modules looking for: Https://pypi.python.org/pypi

5.3python third-party modules

Http://www.cnblogs.com/mmbbflyer/p/5787494.html

Http://www.cnblogs.com/tester-l/p/5735230.html

Python Advanced--02 How to use the module