pip 相关知识

[TOC]
Packages and Module Tutorial
​官方文档​
Demo
层级关系：package —> subpackage —> module —> (class/function/static variable)
import 只能 import 到 module 层级
而 from xxx import xxx 可以 import 最底层
sound/                          Top-level package
      __init__.py               Initialize the sound package
      formats/                  Subpackage for file format conversions
              __init__.py
              wavread.py        # module
              wavwrite.py
              aiffread.py
              aiffwrite.py
              auread.py
              auwrite.py
              ...
      effects/                  Subpackage for sound effects
              __init__.py
              echo.py
              surround.py
              reverse.py
              ...
      filters/                  Subpackage for filters
              __init__.py
              equalizer.py
              vocoder.py
              karaoke.py
              ...
__init__.py 作用
The __init__.py files are required to make Python treat the directories as containing packages; this is done to prevent directories with a common name, such as string, from unintentionally hiding valid modules that occur later on the module search path. In the simplest case, __init__.py can just be an empty file, but it can also execute initialization code for the package or set the __all__ variable, described later.
__init__.py会在包被导入的时候进行初始化。
如何导包
Users of the package can import individual modules from the package, for example:
import sound.effects.echo # echo 可以是一个 subpackage 或者是 module(.py),不能是一个类，方法或者变量
This loads the submodule sound.effects.echo. It must be referenced with its full name.
sound.effects.echo.echofilter(input, output, delay=0.7, atten=4)
An alternative way of importing the submodule is:
from sound.effects import echo
This also loads the submodule echo, and makes it available without its package prefix, so it can be used as follows:
echo.echofilter(input, output, delay=0.7, atten=4)
Yet another variation is to import the desired function or variable directly:
from sound.effects.echo import echofilter # echofilter 可以是一个 subpackage, submodule，也可以是一个方法，一个类，或者一个变量
Again, this loads the submodule echo, but this makes its function echofilter() directly available:
echofilter(input, output, delay=0.7, atten=4)
Note that when using from package import item, the item can be either a submodule (or subpackage) of the package, or some other name defined in the package, like a function, class or variable. The import statement first tests whether the item is defined in the package; if not, it assumes it is a module and attempts to load it. If it fails to find it, an ImportError exception is raised.
Contrarily, when using syntax like import item.subitem.subsubitem, each item except for the last must be a package; the last item can be a module or a package but can’t be a class or function or variable defined in the previous item.
__all__
all 用来限定我 from <module> import * 时，对外暴露哪些模块和变量，起到隐私保护的作用。
It is a list of strings defining what symbols in a module will be exported when from <module> import * is used on the module.
For example, the following code in a foo.py explicitly exports the symbols bar and baz:
__all__ = ['bar', 'baz']
​
waz = 5
bar = 10
def baz(): return 'baz'
These symbols can then be imported like so:
from foo import *
​
print(bar)
print(baz)
​
# The following will trigger an exception, as "waz" is not exported by the module
print(waz)
If the __all__ above is commented out, this code will then execute to completion, as the default behaviour of import * is to import all symbols that do not begin with an underscore, from the given namespace.
Reference: https://docs.python.org/tutorial/modules.html#importing-from-a-package
NOTE: __all__ affects the from <module> import * behavior only. Members that are not mentioned in __all__ are still accessible from outside the module and can be imported with from <module> import <member>.
import * from a package
最终结论：不要使用 import *
from sound.effects import *
实际上，import * 并不会把所有的 submodule 全部导入，真正的导入规则如下：
1.如果 sub-package: effects 下的 __init__.py 文件定义了一个 ist called __all__:
__all__ = ["echo", "surround", "reverse"]
那么只会导入 __all__ 中指定的包，也就是所， from sound.effects import * 只会导入 effects 下的三个 submodule.
2.如果没有定义 __all__变量，那么就会导入 effects 中的所有包
intra-import, relative import
如果 sound.filters.vocoder module 想要使用 sound.effects.echo模块，因为他们都在 sound package 下，所以可以直接引用: from sound.effects import echo
也可以使用相对地址的引用方式
from . import echo
from .. import formats
from ..filters import equalizer
Note that relative imports are based on the name of the current module.
Python 打包发布
​官方教程​
​官方详细教程​
​Setup 教程​
​Github Demo​
上传到官方库的命令：
pip install wheel
python setup.py sdist bdist_wheel # 生成 package
twine upload dist/* # 上传到官方库
Python Pip Tutorial
Note
用 pip 导包的时候，可能报名并不是 import 名称，例如 dateutil 包，pip 的时候就要导入 pip install python-dateutil
pip install
pip install django # 会安装最新的包
pip install django==1.8.2 # 安装特定版本的包
​
pip install -r requirement.txt # 根据环境配置文件导包
pip list
pip list # 输出所有的包
pip freeze
pip freeze > requirement.txt # 导出所有的包
pip 升级
pip install --upgrade 包名 # 升级包
pip install --upgrade django==1.11 # 升级到指定保本
pip uninstall
pip uninstall xxx
Python 虚拟环境
pipenv
官方介绍：https://pypi.org/project/pipenv/
是 pip 和 virtualenv 的组合。
virtualenv
​廖雪峰教程​
virtualenv 用来创建一个虚拟的 python 开发环境
pip install virtualenv # 安装该包
​
# 前提系统应该已经安装了 Python3.7，如果没有安装，则需要 apt-get install python3.7
virtualenv venv --python=python3.7 # 创建一个虚拟的 python 环境，指定 python3.7 的版本
# venv 是 环境所在的文件夹，--python 用于指定 python 版本
​
source venv/bin/activate # 进入该虚拟环境
deactivate # 退出该虚拟环境
​
# 删除一个虚拟环境，只需要删除其文件夹即可
​
# windows 版本：
venv\Scripts\activate 
deactivate
Python Packages
Selenium
Windows Anaconda conf:
1. conda install selenium 或者 pip
2. 下载 chromedriver.exe ,在附件中
3. 将 chromedriver.exe 放到 Anaconda 的目录下，就是第一层目录
4. 将 Chrome 浏览器的目录放在 PATH 变量里，目录可以右击图标链接找到：C:\Users\wanshuo\AppData\Local\Google\Chrome\Application
5. 将 chromedriver.exe 放到 Chrome 浏览器所在目录中，即 Application 中
​
Chrome 版本 要和 ChromeDriver 版本匹配：https://blog.csdn.net/ezreal_tao/article/details/80808729
Linux conf:
1. pip install selenium==2.48.0
2. 安装Chrome
dateutil parser
将时间字符串解析成 datetime
安装
    pip install python-dateutil
​
导包
    from dateutil import parser
​
使用
    dateStruct = parser.parse(date_str)
json
加载 json 文件
import json
def load_json(path):
    try:
        with open(path) as json_file:
            my_dict = json.load(json_file)
    except Exception as e:
        print 'load_dict', e
    finally:
        return my_dict
写入 json 文件
def store_dict(path, data):
    result = True
    try:
        with open(path, 'w') as json_file:
            json_file.write(json.dumps(data))
    except Exception as e:
        print 'store_dict', e
        result = False
    finally:
        return result
json dumps 将字典转成 json 字符串，一行 dumps2string
import json
data = {
    'name' : 'ACME',
    'shares' : 100,
    'price' : 542.23
}
​
json_str = json.dumps(data)
# '{"price": 542.23, "name": "ACME", "shares": 100}'
json loads loads2dict
将 json 编码的字符串转换成一个 python 的数据结构，往往是 dict
json dump, load 用于 读取 和 写入 json 文件。
如果你要处理的是文件而不是字符串，你可以使用 json.dump() 和 json.load() 来编码和解码JSON数据。
# Writing JSON data
with open('data.json', 'w') as f:
    json.dump(data, f)
​
# Reading data back
with open('data.json', 'r') as f:
    data = json.load(f)
汉字转拼音 pinyin
pip install pinyin
​
https://pypi.org/project/pinyin/
​
import pinyin
pinyin.get("你好") # nǐhǎo
wordcloud 词云
生成词云
# pip install wordcloud
import matplotlib.pyplot as plt
from wordcloud import WordCloud
# 读取整个文本
text = open(path.join(d, 'constitution.txt')).read()
# 生成一个词云图像
wordcloud = WordCloud(max_font_size=66).generate(text)
plt.figure()
plt.imshow(wordcloud, interpolation="bilinear")
plt.axis("off")
plt.show()
​
# 参考：https://blog.csdn.net/qq_34337272/article/details/79552929
BeautifulSoup4
官方文档：BeautifulSoup​
fixed problems
1.解析出文档树出问题
这可能是因为 html 源码存在不规范的地方，而 html.parser 解析器的容错率不高，所以导致了解析出错
解决的方法：
# 注意 pip instal lxml
soup = BeautifulSoup(html, "lxml")
commands, subprocess
commands
import commands
cmd = "mkdir test" # 建立 test 文件夹
commands.getstatusoutput(cmd) # 获取 cmd 执行结果的 status 和 output，返回一个元组(status, output)，如果执行成功，则 status 为0，如果命令执行失败，则返回一个非 0 的数字，output 为程序执行完的结果。
Python3.0 以后，commands 被 subprocess 取代。
subprocess
The subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace several older modules and functions:
os.system
os.spawn*
os.popen*
popen2.*
commands.*
Demo:
subprocess.getstatusoutput("cmd") # 返回 0 表示运行成功，返回 非0 表示失败
实际上，在代码上，subprocess 可以直接替代 commands

书籍：python-hacker

JavaWeb 学习笔记

Last modified 1yr ago

pip 相关知识

Packages and Module Tutorial

Demo

`init.py 作用`

如何导包

`all`

import * from a package

intra-import, relative import

Python 打包发布

Python Pip Tutorial

Note

pip install

pip list

pip freeze

pip 升级

pip uninstall

Python 虚拟环境

pipenv

virtualenv

Python Packages

Selenium

dateutil parser

json

汉字转拼音 pinyin

wordcloud 词云

BeautifulSoup4

commands, subprocess