模块简介

Python模块自信：开放

Python是一个开放的系统。

1.编写模块

>>> math.poe(3,2)
Traceback (most recent call last):
  File "<pyshell#29>", line 1, in <module>
    math.poe(3,2)
AttributeError: module 'math' has no attribute 'poe'
>>> math.pow(3,2)
9.0
>>> 

这里math十Python标准库中一个，用import引入，然后可以使用。

1.1模块是程序

模块就是一个Python程序，在需要它的时候将其引用过来。

如果我们自己写一个文件能不能作为模块引用呢

先命名一个Python文件’pm.py‘

lang = 'Python'

>>> 
 RESTART: C:/Users/Administrator/AppData/Local/Programs/Python/Python36-32/pm.py 
>>> import sys>>> sys.path.append('C:/Users/Administrator/AppData/Local/Programs/Python/Python36-32/pm.py')
>>> import pm
>>> pm.lang
'Python'
>>> 

需要告诉Python解释器我们模块的位置（用import sys）然后就可以调用我们自定义的模块了。

 1.2模块的位置

为了让写的模块能被Python解释器知道，需要用sys.path.append。其实，在Python中，所有可引用的模块加入到 sys.path里面了。

>>> import sys
>>> import pprint
>>> pprint.pprint(sys.path)
['C:/Users/Administrator/AppData/Local/Programs/Python/Python36-32',
 'C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32\Lib\idlelib',
 'C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32\python36.zip',
 'C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32\DLLs',
 'C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32\lib',
 'C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32',
 'C:\Users\Administrator\AppData\Local\Programs\Python\Python36-32\lib\site-packages',
 'C:/Users/Administrator/AppData/Local/Programs/Python/Python36-32/pm.py']
>>> 

上面位置内的.py文件都可以作为模块引入。

1.3--al--在模块中的作用

__all__ = ['__privata_variable','public_teacher']

public_variable = '我是public_variable'
_privata_variable = '我是privata variable'

def public_teacher():
    print('我是public')
def _privata_teacher():
    print('我是privata')

>>> import sys
>>> sys.path.append ('C:/Users/Administrator/AppData/Local/Programs/Python/Python36-32/pp.py')
>>> import pp
>>> from pp impport *
SyntaxError: invalid syntax
>>> from pp import *
>>> public_variable
'我是public_variable'
>>> _privata_variable
'我是privata variable'
>>> public_teacher()
我是public
>>> _privata_teacher()
我是privata
>>> 

1.4包和库

 顾名思义，包和库比模块大。Python标准库中的每个库都有好几个包，每个包有若干个模块。

 2标准库概述

安装Python时默认已经安装好的模块被统称为标准库。

2.1 引用的方式

>>> import pprint
>>> from pprint import pprint
>>> from pprint import *
>>> import pprint as pr
>>> from pprint import pprint as pt

2.2 帮助，文档和源码

Python模块的属性和方法是大部分都难以记忆的，所以需要查询（dir()，help()）

>>> import pprint
>>> print(pprint.__doc__)
Support to pretty-print lists, tuples, & dictionaries recursively.

Very simple, but useful, especially in debugging data structures.

Classes
-------

PrettyPrinter()
    Handle pretty-printing operations onto a stream using a configured
    set of formatting parameters.

Functions
---------

pformat()
    Format a Python object into a pretty-printed representation.

pprint()
    Pretty-print a Python object to a stream [default is sys.stdout].

saferepr()
    Generate a 'standard' repr()-like value, but protect against recursive
    data structures.


>>> dir(pprint)
['PrettyPrinter', '_StringIO', '__all__', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', '_builtin_scalars', '_collections', '_perfcheck', '_recursion', '_safe_key', '_safe_repr', '_safe_tuple', '_sys', '_types', '_wrap_bytes_repr', 'isreadable', 'isrecursive', 'pformat', 'pprint', 're', 'saferepr']
>>> help(pprint)
Help on module pprint:

NAME
    pprint - Support to pretty-print lists, tuples, & dictionaries recursively.

DESCRIPTION
    Very simple, but useful, especially in debugging data structures.
    
    Classes
    -------
    
    PrettyPrinter()
        Handle pretty-printing operations onto a stream using a configured
        set of formatting parameters.
    
    Functions
    ---------
    
    pformat()
        Format a Python object into a pretty-printed representation.
    
    pprint()
        Pretty-print a Python object to a stream [default is sys.stdout].
    
    saferepr()
        Generate a 'standard' repr()-like value, but protect against recursive
        data structures.

CLASSES
    builtins.object
        PrettyPrinter
    
    class PrettyPrinter(builtins.object)
     |  Methods defined here:
     |  
     |  __init__(self, indent=1, width=80, depth=None, stream=None, *, compact=False)
     |      Handle pretty printing operations onto a stream using a set of
     |      configured parameters.
     |      
     |      indent
     |          Number of spaces to indent for each level of nesting.
     |      
     |      width
     |          Attempted maximum number of columns in the output.
     |      
     |      depth
     |          The maximum depth to print out nested structures.
     |      
     |      stream
     |          The desired output stream.  If omitted (or false), the standard
     |          output stream available at construction will be used.
     |      
     |      compact
     |          If true, several items will be combined in one line.
     |  
     |  format(self, object, context, maxlevels, level)
     |      Format object for a specific context, returning a string
     |      and flags indicating whether the representation is 'readable'
     |      and whether the object represents a recursive construct.
     |  
     |  isreadable(self, object)
     |  
     |  isrecursive(self, object)
     |  
     |  pformat(self, object)
     |  
     |  pprint(self, object)
     |  
     |  ----------------------------------------------------------------------
     |  Data descriptors defined here:
     |  
     |  __dict__
     |      dictionary for instance variables (if defined)
     |  
     |  __weakref__
     |      list of weak references to the object (if defined)

FUNCTIONS
    isreadable(object)
        Determine if saferepr(object) is readable by eval().
    
    isrecursive(object)
        Determine if object requires a recursive representation.
    
    pformat(object, indent=1, width=80, depth=None, *, compact=False)
        Format a Python object into a pretty-printed representation.
    
    pprint(object, stream=None, indent=1, width=80, depth=None, *, compact=False)
        Pretty-print a Python object to a stream [default is sys.stdout].
    
    saferepr(object)
        Version of repr() which can handle recursive data structures.

DATA
    __all__ = ['pprint', 'pformat', 'isreadable', 'isrecursive', 'saferepr...

FILE
    c:usersadministratorappdatalocalprogramspythonpython36-32libpprint.py