str='Monday is a busy day' 
print(str[0:7]) #表示取第一个到第七个的字符串 
print(str[-3:]) #表示取从倒数第三个字符开始到结尾的字符串 
print(str[::])  #复制字符串 

line='*'*30 
print(line) 
****************************** 

phone='400-800-800-1234' 
print(phone.split('-')) 
['400', '800', '800', '1234'] 

line='hello world; python, I ,like,  it' 
import re 
print(re.split(r'[;,s]\s*',line)) 
>['hello world', 'python', 'I ', 'like', 'it'] 

str1='Hello' 
str2='World' 
new_str=str1+str2 
print(new_str) 
>HelloWorld 

url=['www','python','org'] 
print('.'.join(url)) 
>www.python.org 

filename='trace.h' 
print(filename.endswith('h')) 
True 
print(filename.startswith('trace')) 
True 

str1 = "this is string example....wow!!!" 
str2 = "exam" 
print(str1.find(str2))   # 15 
print(str1.find(str2, 10)) # 15 
print(str1.find(str2, 40)) # -1 

mydate='11/27/2016' 
import re 
if re.match(r'\d+/\d+/\d+',mydate): 
  print('ok.match') 
else: 
  print('not match') 
 
>ok.match 

str = "thing example....wow!!!" 
print(str.count('i', 0, 5)) # 1 
print(str.count('e')) # 2 

text='python is an easy to learn,powerful programming language.' 
print(text.replace('learn','study')) 
>python is an easy to study,powerful programming language. 

students='Boy 103,girl 105' 
import re 
print(re.sub(r'\d+','100',students)) 
>Boy 100,girl 100 

str = ' python str ' 
print(str) 
# 去首尾空格 
print(str.strip()) 
# 去左侧空格 
print(str.lstrip()) 
# 去右侧空格 
print(str.rstrip()) 

instr = 'to' 
outstr = 'TO' 
old_str = 'Hello world , welcome to use Python. 123456' 
remove = '12345' 
table = str.maketrans(instr,outstr,remove) 
new_str = old_str.translate(table) 
print(new_str) 
>HellO wOrld , welcOme TO use PyThOn. 6