摘要：第二章學習流程圖函數轉換為模塊函數轉換為模塊后，就可以靈活的使用模塊，方便代碼分類，避免代碼堆積在一個文件上。使用命令打包代碼，生成發布包打包后會生成目錄和文件發布后會多了目錄和文件，這個是發布的生成的包和相關配置文件。

head first python（第二章）--學習流程圖

函數轉換為模塊后，就可以靈活的使用模塊，方便代碼分類，避免代碼堆積在一個文件上。當你寫的python代碼達到一定數量并且功能開始豐富的時候，就必須要這么做了。而模塊會存在python本地副本目錄里面，所以需要打包，需要安裝模塊到副本目錄，以便python解釋器能夠找到模塊，然后使用。

python搜索模塊的目錄位置：（大致需要知道就行了）

python

Python 2.6.6 (r266:84292, Jan 22 2014, 09:37:14) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.path
["", "/usr/lib/python26.zip", "/usr/lib/python2.6", "/usr/lib/python2.6/plat-linux2", "/usr/lib/python2.6/lib-tk", "/usr/lib/python2.6/lib-old", "/usr/lib/python2.6/lib-dynload", "/usr/lib/python2.6/site-packages"]
>>> 

創建目錄nester

mkdir nester

進入nester目錄并創建nester.py 和setup.py

cd netster

vi nester.py

"""This is the "nester.py" module and it provides one function called print_lol() 
    which prints lists that may or may not include nested lists."""

def print_lol(the_list):
    """This function takes one positional argument called "the_list", which 
        is any Python list (of - possibly - nested lists). Each data item in the 
        provided list is (recursively) printed to the screen on it’s own line."""

for each_item in the_list:
    if isinstance(each_item, list):
        print_lol(each_item)
    else:
        print(each_item)

nester.py代碼模塊文件，格式要嚴謹，不必加上其他的東西。

vi setup.py

from distutils.core import setup

setup( 
    name         = "nester", 
    version      = "1.0.0", 
    ## TODO: be sure to change these next few lines to match your details!
    py_modules   = ["nester"],
    author       = "hfpython",
    author_email = "hfpython@headfirstlabs.com",
    url          = "http://www.headfirstlabs.com",
    description  = "A simple printer of nested lists",
 )

setup.py是模塊發布的元文件metafile，里面包含模塊的一些發布信息。按照格式和要求編寫即可。

python setup.py sdist
running sdist
warning: sdist: manifest template "MANIFEST.in" does not exist (using default file list)
warning: sdist: standard file not found: should have one of README, README.txt
writing manifest file "MANIFEST"
creating nester-1.0.0
making hard links in nester-1.0.0...
hard linking nester.py -> nester-1.0.0
hard linking setup.py -> nester-1.0.0
creating dist
tar -cf dist/nester-1.0.0.tar nester-1.0.0
gzip -f9 dist/nester-1.0.0.tar
tar -cf dist/nester-1.0.0.tar nester-1.0.0
gzip -f9 dist/nester-1.0.0.tar
removing "nester-1.0.0" (and everything under it)

打包后會生成目錄dist和文件MANIFEST

├── dist
│?? └── nester-1.0.0.tar.gz
├── MANIFEST
├── nester.py
└── setup.py

cat MANIFEST

nester.py
setup.py

  
發布后會多了dist目錄和MANIFEST文件，這2個是發布的生成的包和相關配置文件。

python setup.py install

running install
running build
running build_py
copying nester.py -> build/lib
running install_lib
copying build/lib/nester.py -> /usr/lib/python2.6/site-packages
byte-compiling /usr/lib/python2.6/site-packages/nester.py to nester.pyc
running install_egg_info
Removing /usr/lib/python2.6/site-packages/nester-1.0.0-py2.6.egg-info
Writing /usr/lib/python2.6/site-packages/nester-1.0.0-py2.6.egg-info

安裝后

.
├── build
│?? └── lib
│?? └── nester.py
├── dist
│?? └── nester-1.0.0.tar.gz
├── MANIFEST
├── nester.py
└── setup.py

  
安裝后悔出現build目錄，這個就是用發布包解壓出來的庫和模塊代碼，會統一放到python的模塊搜索目錄里面去。

不過出現了錯誤

>>> import nester
>>> print_lol(a)
Traceback (most recent call last):
  File "", line 1, in 
NameError: name "print_lol" is not defined
>>> 

  
是因為命名空間的關系,主python程序中（以及idle shell中）的代碼與一個名為main的命名空間關聯。所以的話不能直接使用print_lol，而要加上命名空間nester.print_lol()

知識點：

1.命名空間是為了讓python解釋器就會知道去哪里找這個函數，命名空間格式：首先是模塊名字，然后是一個點號，再后面是函數名。

2.如果使用from nester import print_lol,就會把指定的函數print_lol增加到當前命名空間中，這樣就不用加上命名空間來調用函數了。

這樣可以增加功能而不用增加多余函數代碼（print_lol2）。

  
寫新代碼之前先考慮BIF（內置函數）

  
rang() 返回一個迭代器，根據需要生成一個指定范圍的數字。

根據需求寫了這樣的代碼，但運行報錯
增加了一個level參數，默認等于0，遇到嵌套列表就是用rang（level）來進行縮進

def print_lol(a_list, level=0):
    """Prints each item in a list, recursively descending
    into nested lists (if necessary)."""

for each_item in a_list:
    if isinstance(each_item, list):
        print_lol(each_item, level)
    else:
        for l in range(level):
            print("	", end="")
        print(each_item)

出現錯誤了：TypeError:print_lol() take exactly 2 positional arguments (1 given)

原因是print_lol需要2個參數，目前只有一個。

要改成

def print_lol(a_list, level=0):
    """Prints each item in a list, recursively descending
    into nested lists (if necessary)."""

for each_item in a_list:
    if isinstance(each_item, list):
        print_lol(each_item, level+1)  #因為不加1的話函數調用還是會出現level=0，就沒有意義了
    else:
        for l in range(level):
            print("	", end="")
        print(each_item)

然后更新代碼發布包

from distutils.core import setup

setup( 
    name         = "nester", 
    version      = "1.1.0",     #這里改成1.1.0了，更新了新代碼版本
    ## TODO: be sure to change these next few lines to match your details!
    py_modules   = ["nester"],
    author       = "hfpython",
    author_email = "hfpython@headfirstlabs.com",
    url          = "http://www.headfirstlabs.com",
    description  = "A simple printer of nested lists",
 )

因為增加了level參數，改變了默認的行為（最原始的默認行為不想要縮進），導致打印出來的格式有異常，需要再增加一個可選參數，來控制縮進功能的使用。

增加一個indent參數來控制縮進是否打開

def print_lol(a_list, indent=False, level=0):
    """Prints each item in a list, recursively descending
    into nested lists (if necessary)."""

for each_item in a_list:
    if isinstance(each_item, list):
        print_lol(each_item, indent, level+1)
    else:
        if indent:
            for l in range(level):
                print("	", end="")
        print(each_item)

  
需要注意的是所有代碼如果不是idel中運行的話，都需要加上#!/usr/bin/python在頂部。

原文鏈接：http://www.godblessyuan.com/2015/04/13/head_first_python_chapter_2_lea...