> str=[1,2,3,4,5,2,6]
> str.remove(2)
> str
[1, 3, 4, 5, 2, 6]

> str=[0,1,2,3,4,5,6]
> str.pop(1)  #pop删除时会返回被删除的元素
1
> str
[0, 2, 3, 4, 5, 6]
> str2=['abc','bcd','dce']
> str2.pop(2)
'dce'
> str2
['abc', 'bcd']

> str=[1,2,3,4,5,2,6]
> del str[1]
> str
[1, 3, 4, 5, 2, 6]
> str2=['abc','bcd','dce']
> del str2[1]
> str2
['abc', 'dce']

> str=[0,1,2,3,4,5,6]
> del str[2:4] #删除从第2个元素开始，到第4个为止的元素(但是不包括尾部元素)
> str
[0, 1, 4, 5, 6]

> str=[0,1,2,3,4,5,6]
> del str
> str     #删除后，找不到对象
Traceback (most recent call last):
 File "<pyshell#27>", line 1, in <module>
  str
NameError: name 'str' is not defined

s1=(1,2,3,4,5,6)
s2=(2,3,5)
s3=[]
for i in s1:
if i not in s2:
  s3.append(i)
print 's1-1:',s1
s1=s3
print 's2:',s2
print 's3:',s3
print 's1-2:',s1