1、类
学过面向对象编程的想必对类这个东西并不陌生，类是封装对象的属和行为的载体，比如说人类、鸟类，这些都是泛指一类。如果从人类中特指出一个人xxx，那xxx人必定会有人类这个类的相应的特征，xxx人就是一个对象，而由类到具体对象的过程称之为实例化。
1.1 类方法
方法可以理解为函数，在类中定义方法必须要加入参数self,它表示的是实例化的对象，如以下语句，表示为实例化添加静态的属性name
self.name = name
除了上面的添加属性以外，还有一种添加属性的方法，不过有所不同
self.__age = age //__age 实例化后不会被修改，要通过方法去改变，即实例化时传参
下面通过例子来看
class Student():
def __init__(self,name,age):
self.name = name
self.__age = age
def print_inform(self):
print("name is %s" % self.name)
print("age is %d" % self.__age)
user = Student("user1",15)
user.print_inform()
user.name = "Tom"
user.__age = 20
user.print_inform()
1.2 继承
继承就是提高代码重用度的一种方法，代码如下：
class Father():
def __init__(self,name,age=30):
self.name = name
self.age = age
def print_inform(self):
print("name is %s" % self.name)
print("age is %d" % self.age)
class Son_1(Father): //继承父类的方法
pass
class Son_2(Father):
def __init__(self,name,age):
super().__init__(name,age)
a1 = Father("Tom",60)
a1.print_inform()
a2 = Son_1("jon",15)
a2.print_inform()
a3 = Son_2("A",10)
a3.print_inform()
结果
name is Tom
age is 60
name is jon
age is 15
name is A
age is 10
2、 with
除了常见的使用with打开文件外，with最大的作用就是处理异常
class Test_with():
def __enter__(self):
print("start")
def __exit__(self, type, value, trace):
print("exit")
with Test_with():
print("runing")
class Test_with():
def __enter__(self):
print("start")
def __exit__(self, type, value, trace):
if trace is None:
print("exit")
else:
print("error is %s" % trace)
with Test_with():
print("runing")
raise NameError("testNameError")
3、并发
3.1 threading库
import threading
import time
from threading import current_thread
def Thread_test(arg1,arg2):
print(current_thread().getName(),"start")
print("%s %s" %(arg1,arg2))
time.sleep(1)
print(current_thread().getName(),"stop")
for i in range(1,6,1):
t1 = threading.Thread(target=Thread_test,args=(i,i+1))
t1.start()
print(current_thread().getName(),"end")
结果
Thread-6 start
1 2
Thread-7 start
2 3
Thread-8 start
3 4
Thread-9 start
4 5
Thread-10 start
MainThread 5 6
end
Thread-6 stop
Thread-7 stop
Thread-8 stop
Thread-9 stop
Thread-10 stop
3.2 实现线程同步
import threading
from threading import current_thread
class Test_thread(threading.Thread):
def run(self):
print(current_thread().getName(),"start")
print("run")
print(current_thread().getName(),"stop")
t1 = Test_thread()
t1.start()
t1.join()
print(current_thread().getName(),"end")
结果
Thread-6 start
run
Thread-6 stop
MainThread end
4、时间 datetime and time
4.1 time库
>>> import time
>>> print(time.localtime())
time.struct_time(tm_year=2019, tm_mon=3, tm_mday=4, tm_hour=15, tm_min=34, tm_sec=1, tm_wday=0, tm_yday=63, tm_isdst=0)
>>> print(time.strftime("%Y-%m-%d"))
2019-03-04
4.2 datetime库
>>> import datetime
>>> print(datetime.datetime.now())
2019-03-04 15:36:05.637828
>>> newtime = datetime.timedelta(minutes=10)
>>> print(datetime.datetime.now()+newtime)
2019-03-04 15:47:29.401035
>>> one_day = datetime.datetime(2010,5,7)
>>> print(one_day)
2010-05-07 00:00:00
5、数学 math and random
math库可用于常见数学上的运算，如sin，cos等
>>> import random
>>> print(random.randint(1,10)) //输出1~10的随机数
7
>>> print(random.choice(["a","b","c"])) //随机输出a,b,c
a
6、命令行 os
>>> import os
>>> print(os.path.exists("/user")) //判断目录是否存在
False
7、正则re
这一项我以前写过，在正则表达式中
8、python-xml
xml 指可扩展标记语言，它是为了方便数据传输而设计的
<nodes>
<node id="Use the DPID" name="host1" type="host" image="ubuntu:14.04">
<ip>192.168.100.1</ip>
<mac>Use the MAC address</mac>
</node>
<node id="Use the DPID" name="host2" type="host" image="nginx">
<ip>192.168.100.2</ip>
<mac>Use the MAC address</mac>
</node>
</nodes>
标签语言，有tag、attrib、text
import xml.etree.ElementTree as ET
tree = ET.parse('country_data.xml')
root = tree.getroot()
9、python-json
>>>import json
>>>data = json.loads(topo) //loads中s代表string
>>>data = json.dumps(topo)
10、 subprocess
import subprocess
run(...): Runs a command, waits for it to complete, then returns a CompletedProcess instance.
Popen(...): A class for flexibly executing a command in a new process
subprocess.Popen("D:\\Evernote\\Evernote\\Evernote.exe")
subprocess.Poprn("D:\\Python\\Python36\\python3.exe","C:\\hello.py")
Popen对象有两个方法poll()、wait()
11、 PIL
一个用于图片处理的库
from PIL import image
elem = Image.open("demo.jpg")
elem.size
elem.format
elem.filename
im = Image.new("RGBA",(100,200),"purple")
im.save("purple.png")