为了编写可维护的代码，我们把很多函数分组， 在python中一个.py 文件就是一个模块
好处
1 提高可维护性
2 可重用
3 避免函数名和变量名冲突
模块分为3种
1 内置标准模块（标准库） 执行help(‘modules’)查看所有python 自带模块
2 第三方模块 通过pip install模块名联网安装
3 自定义模块
#自带和从第三方下载的模块 '_'不用管主要看不带'_'的
>>> help('modules')
Please wait a moment while I gather a list of all available modules...
__future__ _strptime fnmatch reprlib
_abc _struct formatter rlcompleter
_ast _symtable fractions runpy
_asyncio _testbuffer ftplib sched
_asyncio_d _testbuffer_d functools secrets
_bisect _testcapi gc select
_blake2 _testcapi_d genericpath select_d
_bootlocale _testconsole getopt selectors
_bz2 _testconsole_d getpass setuptools
_bz2_d _testimportmultiple gettext shelve
_codecs _testimportmultiple_d glob shlex
_codecs_cn _testmultiphase gzip shutil
_codecs_hk _testmultiphase_d hashlib signal
_codecs_iso2022 _thread heapq site
_codecs_jp _threading_local hmac smtpd
_codecs_kr _tkinter html smtplib
_codecs_tw _tkinter_d http sndhdr
_collections _tracemalloc idlelib socket
_collections_abc _warnings imaplib socketserver
_compat_pickle _weakref imghdr sqlite3
_compression _weakrefset imp sre_compile
_contextvars _winapi importlib sre_constants
_contextvars_d abc inspect sre_parse
_csv aifc io ssl
_ctypes antigravity ipaddress stat
_ctypes_d argparse itertools statistics
_ctypes_test array json string
_ctypes_test_d ast keyword stringprep
_datetime asynchat lib2to3 struct
_decimal asyncio linecache subprocess
_decimal_d asyncore locale sunau
_distutils_findvs atexit logging symbol
_distutils_findvs_d audioop lzma symtable
_dummy_thread base64 macpath sys
_elementtree bdb mailbox sysconfig
_elementtree_d binascii mailcap tabnanny
_functools binhex marshal tarfile
_hashlib bisect math telnetlib
_hashlib_d builtins mimetypes tempfile
_heapq bz2 mmap test
_imp cProfile modulefinder textwrap
_io calendar msilib this
_json cgi msvcrt threading
_locale cgitb multiprocessing time
_lsprof chunk netrc timeit
_lzma cmath nntplib tkinter
_lzma_d cmd nt token
_markupbase code ntpath tokenize
_md5 codecs nturl2path trace
_msi codeop numbers traceback
_msi_d collections opcode tracemalloc
_multibytecodec colorsys operator tty
_multiprocessing compileall optparse turtle
_multiprocessing_d concurrent os turtledemo
_opcode configparser parser types
_operator contextlib pathlib typing
_osx_support contextvars pdb unicodedata
_overlapped copy pickle unicodedata_d
_overlapped_d copyreg pickletools unittest
_pickle crypt pip urllib
_py_abc csv pipes uu
_pydecimal ctypes pkg_resources uuid
_pyio curses pkgutil venv
_queue dataclasses platform warnings
_queue_d datetime plistlib wave
_random dbm poplib weakref
_sha1 decimal posixpath webbrowser
_sha256 difflib pprint winreg
_sha3 dis profile winsound
_sha512 distutils pstats winsound_d
_signal doctest pty wsgiref
_sitebuiltins dummy_threading py_compile xdrlib
_socket easy_install pyclbr xml
_socket_d email pydoc xmlrpc
_sqlite3 encodings pydoc_data xxsubtype
_sqlite3_d ensurepip pyexpat zipapp
_sre enum pyexpat_d zipfile
_ssl errno queue zipimport
_ssl_d faulthandler quopri zlib
_stat filecmp random
_string fileinput re
Enter any module name to get more help. Or, type "modules spam" to search
for modules whose name or summary contain the string "spam".导入模块
import module
from module import xx
from module.xx.xx import xx as rename
from module.xx.xx import *注意：模块一旦被调用，即相当于执行了另一个py文件里的代码
举例
>>> import random #1
>>>> random.randint(0,100)
41
>>> random.randint(0,100)
11
>>> random.randint(0,100)
7
>>>
>>> import os #2
>>> from os import rmdir,rename
>>>
from django.core import handers
import socket
form socket import * (不建议)
模块的导入路径
开源模块学习的安装方式
http://pypi.python.org/pypi
注册一个账号即可上传
python3 setup.py build
install
使用国内源下载模块
pip3 install -i http://pypi.douban.com/simple/paramiko --trusted-host pypi.douban.com 包及跨模块导入1
包 package
当你的模块越来越多的时候，就需要对模块文件进行划分，比如把负责跟数据库交互的都放一个文件夹，把与页面交互相关的放一个文件夹
一个文件夹管理多个模块文件，这个文件夹就叫包
加个init.py文件就会把目录初始化成一个包
python3默认
跨模块导入2
import sys
import os
print(dir())
print(__file__)
BASE_DIR = os.path.dirname(os.path.dirname(__file__))
print(BASE_DIR)
# print(sys.path)
# from proj import settings
def sayhi(name):
print('hello',name)
sayhi('alex')
相对导入
文件夹被python解释器视作package需要满足一下两个条件：
1 文件夹中必须有init.py文件，该文件可以为空，但必须存在该文件
2不能作为顶层模块来执行该文件夹中的py文件（即不能作为主函数的入口）
所以这个解决办法就是，既然你在views.py里执行了相对导入，那就不要把views当作入口程序，可以通过上一级的manage.py调用views.py
from . import views
from ..proj import settings