python学习笔记-Day6(2)

xml处理模块

xml是实现不同语言或程序之间进行数据交换的协议,跟json差不多,但json使用起来更简单,不过,古时候,在json还没诞生的黑暗年代,大家只能选择用xml呀,至今很多传统公司如金融行业的很多系统的接口还主要是xml。

import xml.etree.ElementTree as ET

tree = ET.parse("country.xml")
root = tree.getroot() # 获得根节点 print(root.tag) # 遍历xml文档
for child in root:
print(child.tag,child.attrib)
for i in child:
print("-->",i.tag,i.text)
import xml.etree.ElementTree as ET

tree = ET.parse("country.xml")
root = tree.getroot() # get the root node #只获得year节点
for node in root.iter('year'):
print(node.tag,node.text)

  

#修改

for node in root.iter('year'):
new_year = int(node.text)+1
node.text = str(new_year)
node.set("updated","yes")
tree.write("xml_test2.xml")

  

#删除

for country in root.findall("country"):
rank = int(country.find('rank').text)
if rank > 50:
root.remove(country)
tree.write("xml_test2.xml")

  

#create
new_xml = ET.Element("namelist")#root
name = ET.SubElement(new_xml,"name",attrib={"enrolled":"yes"})
age = ET.SubElement(name,"age",attrib={"checked":"no"})
sex = ET.SubElement(name,"sex")
sex.text = '33'
name2 = ET.SubElement(new_xml,"name",attrib={"enrolled":"no"})
age = ET.SubElement(name2,"age")
age.text = '19' et = ET.ElementTree(new_xml) #生成文档对象
et.write("new_test.xml", encoding="utf-8",xml_declaration=True) ET.dump(new_xml) #打印生成的格式

  

ConfigParser模块

用于生成和修改常见配置文档

[DEFAULT]
ServerAliveInterval = 45
Compression = yes
CompressionLevel = 9
ForwardX11 = yes [bitbucket.org]
User = hg [topsecret.server.com]
Port = 50022
ForwardX11 = no

对配置文件操作

#生成配置文件
import configparser
config = configparser.ConfigParser()
config.read('example6.ini')
config["DEFAULT"] = {'ServerAliveInterval': '45',
'Compression': 'yes',
'CompressionLevel': '9'} config['bitbucket.org'] = {}
config['bitbucket.org']['User'] = 'hg'
config['topsecret.server.com'] = {}
topsecret = config['topsecret.server.com']
topsecret['Host Port'] = '50022' # mutates the parser
topsecret['ForwardX11'] = 'no' # same here
config['DEFAULT']['ForwardX11'] = 'yes'
with open('example.ini', 'w') as configfile:
config.write(configfile) # 删除指定模块
sec = config.remove_section('bitbucket.org')
config.write(open('example4.ini','w')) #删除模块下的指定项目
config.remove_option('alan','age')
config.write(open('example6.ini','w')) #判断模块名是否存在不存在就创建
sec = config.has_section('alan')
config.add_section('alan')
config['alan']['age']="21"
config.write(open('example6.ini','w')) #改写模块下的指定项目
config.set('alan','age','22')
config.write(open('example6.ini','w'))

  

hashlib模块  

用于加密相关的操作,3.x里代替了md5模块和sha模块,主要提供 SHA1, SHA224, SHA256, SHA384, SHA512

>>> import hashlib
>>> a =hashlib.md5()
>>> a.update(b"Hello")
>>> a.update(b"it's me")
>>> a.digest() #二进制
b'\xc3\xb8Fk,fV\x9c\xd3\x01\x15\xdf\xd3\x9bd\xb8'
>>> a.hexdigest() #16进制
'c3b8466b2c66569cd30115dfd39b64b8'
>>> b = hashlib.sha512()
>>> b.update(b'Hello')
>>> b.digest()
b'6\x15\xf8\x0c\x9d)>\xd7@&\x87\xf9K"\xd5\x8eR\x9b\x8c\xc7\x91o\x8f\xac\x7f\xdd\xf7\xfb\xd5\xafL\xf7w\xd3\xd7\x95\xa7\xa0\n\x16\xbf~\x7f?\xb9V\x1e\xe9\xba\xaeH\r\xa9\xfez\x18v\x9eq\x88k\x03\xf3\x15'
>>> b.hexdigest()
'3615f80c9d293ed7402687f94b22d58e529b8cc7916f8fac7fddf7fbd5af4cf777d3d795a7a00a16bf7e7f3fb9561ee9baae480da9fe7a18769e71886b03f315'

hmac模块 

python 还有一个 hmac 模块,它内部对我们创建 key 和 内容 再进行处理然后再加密

>>> import hmac
>>> a=hmac.new(b"secret_key")
>>> a.update(b"Hello")
>>> a.digest()
b'RF\r"\xec~@-\xc8\xc6*\xed\xa5\x1e\xc9 '
>>> a.hexdigest()
'52460d22ec7e402dc8c62aeda51ec920'

Subprocess模块

运行python的时候,我们都是在创建并运行一个进程。像Linux进程那样,一个进程可以fork一个子进程,并让这个子进程exec另外一个程序。在Python中,我们通过标准库中的subprocess包来fork一个子进程,并运行一个外部的程序。
subprocess包中定义有数个创建子进程的函数,这些函数分别以不同的方式创建子进程,所以我们可以根据需要来从中选取一个使用。另外subprocess还提供了一些管理标准流(standard stream)和管道(pipe)的工具,从而在进程间使用文本通信。

>>> subprocess.run(["ls", "-l"])  # doesn't capture output
CompletedProcess(args=['ls', '-l'], returncode=0) >>> subprocess.run("exit 1", shell=True, check=True)
Traceback (most recent call last):
...
subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1 >>> subprocess.run(["ls", "-l", "/dev/null"], stdout=subprocess.PIPE)
CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n')

  

调用subprocess.run(...)是推荐的常用方法,在大多数情况下能满足需求,但如果你可能需要进行一些复杂的与系统的交互的话,你还可以用subprocess.Popen(),语法如下:

p = subprocess.Popen("find / -size +1000000 -exec ls -shl {} \;",shell=True,stdout=subprocess.PIPE)
print(p.stdout.read())#显示执行结果

可用参数:

    • args:shell命令,可以是字符串或者序列类型(如:list,元组)
    • bufsize:指定缓冲。0 无缓冲,1 行缓冲,其他 缓冲区大小,负值 系统缓冲
    • stdin, stdout, stderr:分别表示程序的标准输入、输出、错误句柄
    • preexec_fn:只在Unix平台下有效,用于指定一个可执行对象(callable object),它将在子进程运行之前被调用
    • close_sfs:在windows平台下,如果close_fds被设置为True,则新创建的子进程将不会继承父进程的输入、输出、错误管道。
      所以不能将close_fds设置为True同时重定向子进程的标准输入、输出与错误(stdin, stdout, stderr)。
    • shell:同上
    • cwd:用于设置子进程的当前目录
    • env:用于指定子进程的环境变量。如果env = None,子进程的环境变量将从父进程中继承。
    • universal_newlines:不同系统的换行符不同,True -> 同意使用 \n
    • startupinfo与createionflags只在windows下有效
      将被传递给底层的CreateProcess()函数,用于设置子进程的一些属性,如:主窗口的外观,进程的优先级等等

终端输入的命令分为两种:

    • 输入即可得到输出,如:ifconfig
    • 输入进行某环境,依赖再输入,如:python

交互实例

import subprocess

obj =  subprocess.Popen(["python"],stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
obj.stdin.write("print('hello')\n")
obj.stdin.write("print('hello1')\n")
obj.stdin.write("print('hello2')\n")
obj.stdin.write("print('hello3')\n")
out_error_list = obj.communicate()
print(out_error_list)

logging模块 

很多程序都有记录日志的需求,并且日志中包含的信息即有正常的程序访问日志,还可能有错误、警告等信息输出,python的logging模块提供了标准的日志接口,你可以通过它存储各种格式的日志,logging的日志可以分为 debug()info()warning()error() and critical() 5个级别

Level When it’s used
DEBUG Detailed information, typically of interest only when diagnosing problems.
INFO Confirmation that things are working as expected.
WARNING An indication that something unexpected happened, or indicative of some problem in the near future (e.g. ‘disk space low’). The software is still working as expected.
ERROR Due to a more serious problem, the software has not been able to perform some function.
CRITICAL A serious error, indicating that the program itself may be unable to continue running.

 

实例

import logging

logging.basicConfig(filename='example2.log',level=logging.ERROR)#创建日志文件并设定级别
logging.debug('This message should go to the log file') #当级别为debug时打印的信息
logging.info('So should this')
logging.warning('And this, too')#除了level设置为error意外的任何一个级别都会打印

格式化输出

import logging
logging.basicConfig(format='%(asctime)s %(message)s', datefmt='%Y-%m-%d %H:%M:%S ')
logging.warning('is when this event was logged.')

输出文件并输出到屏幕

#create logger

logger = logging.getLogger('TEST-LOG')
logger.setLevel(logging.DEBUG) # create console handler and set level to debug
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG) # create file handler and set level to warning
fh = logging.FileHandler("access.log")
fh.setLevel(logging.WARNING)
# create formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') # add formatter to ch and fh
ch.setFormatter(formatter)
fh.setFormatter(formatter) # add ch and fh to logger
logger.addHandler(ch)
logger.addHandler(fh) # 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')

对于格式,有如下属性可是配置:

python学习笔记-Day6(2)

用于便捷记录日志且线程安全的模块

mport logging

logging.basicConfig(filename='log.log',
format='%(asctime)s - %(name)s - %(levelname)s -%(module)s: %(message)s',
datefmt='%Y-%m-%d %H:%M:%S %p',
level=10) logging.debug('debug')
logging.info('info')
logging.warning('warning')
logging.error('error')
logging.critical('critical')
logging.log(10,'log')

等级:

只有大于当前日志等级的操作才会被记录。

CRITICAL = 50
FATAL = CRITICAL
ERROR = 40
WARNING = 30
WARN = WARNING
INFO = 20
DEBUG = 10
NOTSET = 0

  

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