‘1 2 3'.split()=>['1','2','3']
'1 2 3'.split(None,1)=>['1','2 3']
'1,,2'.split(',')=>['1',''.'2']
我们把可能发生错误的语句放在try模块里，用except来处理异常。except可以处理一个专门的异常，也可以处理一组圆括号中的异常，如果except后没有指定异常，则默认处理所有的异常。每一个try，都必须至少有一个except
try：
pass
except(IOError ,ZeroDivisionError),e
Lambda Expression:
Small anonymous functions can be created with thelambdakeyword. This function returns the sum of its two arguments:lambdaa,b:a+b.Lambdafunctions can be used wherever function objects are required. They are syntactically restricted to a single expression. Semantically, they are just syntactic sugar for a normal function definition. Like nested function definitions, lambda functions can reference variables from the containing scope:
代码
book_list=sorted(book_list,key=lambda x:x[1],reverse=True )
Return a string which is the concatenation of the strings in theiterableiterable. The separator between elements is the string providing this method.
a='/'.join(['a','b','c'])=>'a/b/c'
Python的字典排序：
```
a={'2':10,'3':30,'4':3}
sorted(a.items(),key=lambda x:x[1],reverse=False)
```
```
>>> a=[(1,2),('3','a')]
>>> {x:y for x,y in a}
{'3': 'a', 1: 2}
```
