Python学习

第一个例子

#打开新窗口,输入: 
#! /usr/bin/python 
# -*- coding: utf8 -*-     

s1=input("Input your name:")
print("你好,%s" % s1) 

'''  知识点:
      * input("某字符串")函数:显示"某字符串",并等待用户输入.
      * print()函数:如何打印.
      * 如何应用中文
      * 如何用多行注释 
'''

注意，当使用input函数，输入字符串时，需要使用""将字符串包含起来，否则会报错如下

 Traceback (most recent call last):
    File "<pyshell#1>", line 1, in <module>
     input_A = input("Input: ")
   File "<string>", line 1, in <module>
 NameError: name 'abc' is not defined

第二个例子

#! /usr/bin/python

x={'a':'aaa','b':'bbb','c':12}
print (x['a'])
print (x['b'])
print (x['c'])

for key in x: 
    print ("Key is %s and value is %s" % (key,x[key]))
''' 
知识点:  
    * 将他当Java的Map来用即可. 
''' 

第三个例子

#! /usr/bin/python

word="abcdefg" 
a=word[2]  
print ("a is: "+a) 
b=word[1:3]  
print ("b is: "+b) # index 1 and 2 elements of word.
c=word[:2]  
print ("c is: "+c) # index 0 and 1 elements of word. 
d=word[0:]  
print ("d is: "+d) # All elements of word. 
e=word[:2]+word[2:]  
print ("e is: "+e) # All elements of word. 
f=word[-1]  
print ("f is: "+f) # The last elements of word. 
g=word[-4:-2]  
print ("g is: "+g) # index 3 and 4 elements of word. 
h=word[-2:]  
print ("h is: "+h) # The last two elements. 
i=word[:-2]
print ("i is: "+i) # Everything except the last two charactersz
l=len(word)
print ("Length of word:" + str(l))

条件循环语句

#!/usr/bin/python
#条件和循环语句

x=int(input("Please enter an integer:"))
if x<0:
     x=0
     print ("Negative changed to zero")
elif x==0:
     print ("Zero")
else:
      print ("More")
# Loops List
a = ['cat', 'window', 'defenestrate']
for x in a:
      print (x, len(x))
#知识点:
#    * 条件和循环语句
#    * 如何得到控制台输入

函数

#! /usr/bin/python 
# -*- coding: utf8 -*-    
def sum(a,b): 
    return a+b

func = sum 
r = func(5,6)
print (r)

# 提供默认值
def add(a,b=2):     
    return a+b
r=add(1)
print (r)
r=add(1,5)
print (r)

#返回空，和判断函数返回值是否为空
def voidfunc():
    return None

ret = voidfunc()
if ret is None:
    print 'this function return nothing'

一个好用的函数

#! /usr/bin/python 
# -*- coding: utf8 -*-    
# The range() function 
a =range (1,10) for i in a:
print (i)

a = range(-2,-11,-3) # The 3rd parameter stands for step 
for i in a:
    print (i)

 异常处理

#!/usr/bin/python

s=input("Input your age:")
if s =="":
    raise Exception("Input must no be empty.")  

try:
    i=int(s)

except Exception as err:
    print(err)
finally: # Clean up action
    print("Goodbye!") 

注意：老版本的Python，except语句写作"except Exception, e"，Python 2.6后应写作"except Exception as e"。

 返回值

对于python执行程序完成后，我们需要给程序一个返回值。设置方法如下。

#!/usr/bin/python

import sys
sys.exit(0)

#如果想要检查一个python的返回值，可以如下

import os
ret = os.system('./example.py')
print(ret)

 ConfigParser的使用

#!/usr/bin/env python
import ConfigParser
import sys
config=ConfigParser.ConfigParser()
config.add_section("book1")
config.set("book1","title","hello world")
config.set("book1","aut","log")
config.write(open("f.txt","w"))

config.read("f.txt")
s = config.sections()
print 'section:', s

titile = config.get("book1", "title")

'''
f.txt内容
[book1]
aut = log
title = hello world
'''

 python main解析

#!/usr/bin/env python
#文件名为main.py

def main():
    print "main function runing"

if __name__ == "__main__":
    main()

如果在另一个文件中作为模块调用

#!/usr/bin/env python
#如果有 if __name__ = "__main__": 语句，则无任何打印结果
#反之，则会正常执行main.py
import main

定义自己的模块

  在Python中，每个Python文件都可以作为一个模块，模块的名字就是文件的名字。

#test.py

def display():
    print 'hello world'
    
display()

#调用模块内容
#test1.py

import test

  urllib.unquote(string) ：对字符串进行解码；

data = 'name = ~a+3'  
   
data1 = urllib.quote(data)  
print data1 # result: name%20%3D%20%7Ea%2B3  
print urllib.unquote(data1) # result: name = ~a+3  

data2 = urllib.quote_plus(data)  
print data2 # result: name+%3D+%7Ea%2B3  
print urllib.unquote_plus(data2)    # result: name = ~a+3  
  
data3 = urllib.urlencode({ 'name': 'dark-bull', 'age': 200 })  
print data3 # result: age=200&name=dark-bull  
   
data4 = urllib.pathname2url(r'd:ac23.php')  
print data4 # result: ///D|/a/b/c/23.php  
print urllib.url2pathname(data4)    # result: D:ac23.php  

urlparse 拆分网址为 RFC 中对应的组件。

from urlparse import urlparse
url = ’http://netloc/path;param?query=arg#frag’
parsed = urlparse(url)
print parsed
'''
 执行结果：
 $ python urlparse_urlparse.py
ParseResult(scheme=’http’, netloc=’netloc’, path=’/path’,
params=’param’, query=’query=arg’, fragment=’frag’)
'''

按行读取文件

# File: readline-example-1.py
 
file = open("sample.txt")
 
while 1:
    line = file.readline()
    if not line:
        break
    pass # do something


# File: readline-example-2.py
 
import fileinput
 
for line in fileinput.input("sample.txt"):
    pass

# 带缓存
# File: readline-example-3.py
 
file = open("sample.txt")
 
while 1:
    lines = file.readlines(100000)
    if not lines:
        break
    for line in lines:
        pass # do something

#python 2.2以后可以

# File: readline-example-5.py
 
file = open("sample.txt")
 
for line in file:
    pass # do something


# 而在 python 2.1里面 只能使用如下方法
# File: readline-example-4.py
 
file = open("sample.txt")
 
for line in file.xreadlines():
    pass # do something

 字典dict, 列表, 元组,

'''
字典：dic={'a':12,'b':34}
列表：list=[1,2,3,4]
元组：tup=(1,2,3,4)
'''
#字典操作
dict = {}
dict['name'] = 'poseidon'
# 注意如果使用下行命令读取，会报错 KeyError: 'form_submit'
#print dict['name'] 
#读取方式应该为, noname为默认值
dict.get('name', 'noname') 
#得到最后一个值
last = dict.pop()
#也可以得到第一个值
first = dict.pop(1)

 列表

list[] = ["apple", "banana", "grape", "orange"]
print list[0]

list[] = ["apple", "banana", "grape", "orange"]
print list[0]

#列表求交集
b1=[1,2,3]
b2=[2,3,4]
b3 = [val for val in b1 if val in b2]
print b3

#列表就差集
b3 = [val for val in b1 if val not in b2]
print b3 

#列表排重对rows
rows=list(set(rows))#排重列表