1.字典实例：建立学生学号成绩字典，做增删改查遍历操作。
>>> d={2015001:"75分", 2015002:"95分",2015003:"85分"}
>>> d[201504]="100分"
>>> print("增加后：",d)
增加后： {2015001: '75分', 2015002: '95分', 2015003: '85分', 201504: '100分'}
>>> d.pop(2015001)
'75分'
>>> print("删除后：",d)
删除后： {2015002: '95分', 2015003: '85分', 201504: '100分'}
>>> d[201502]="90分"
>>> print("修改后：",d)
修改后： {2015002: '95分', 2015003: '85分', 201504: '100分', 201502: '90分'}
>>> print("查找学号2015005:",d.get(2015005))
查找学号2015005: None
>>> print("遍历后:", d.items())
遍历后: dict_items([(2015002, '95分'), (2015003, '85分'), (201504, '100分'), (201502, '90分')])
2.列表，元组，字典，集合的遍历。
>>> ls=list('2323121')
>>> ls
['2', '3', '2', '3', '1', '2', '1']
>>> for i in ls:
print(i)
2
3
2
3
1
2
1
>>> tu=tuple('2323121')
>>> tu
('2', '3', '2', '3', '1', '2', '1')
>>> for i in tu:
print(i)
2
3
2
3
1
2
1
>>> d={"a":0,"b":2,"c":3}
>>> d
{'a': 0, 'b': 2, 'c': 3}
>>> for i in d:
print(i,d[i])
a 0
b 2
c 3
>>> se=set('2323121')
>>> se
{'3', '2', '1'}
>>> for i in se:
print(i)
3
2
1
总结列表，元组，字典，集合的联系与区别。
3.英文词频统计实例
1.待分析字符串
2.分解提取单词
1.大小写 txt.lower()
2.分隔符'.,:;?!-_’
3.单词列表
3.单词计数字典
s='''Met you by surprise I didn't realize
That my life would change forever
Saw you standing there
I didn't know I cared,There was something special in the air
Dreams are my reality
The only kind of real fantasy,
illusions are a common thing
I try to live in dreams
It seems as it's meant to be
Dreams are my reality!
A different kind of reality
I dream of loving in the night
And loving seems alright
Although it's only fantasy
If you do exist honey don't resist
Show me a new way of loving
Tell me that it's true
show me what to do
I feel something special about you
Dreams are my reality
The only kind of reality
May be my foolishness is past
And may be now at last
I'll see how the real thing can be
Dreams are my reality! '''
s=s.lower()
for i in ',!':
s=s.replace(i,' ')
s=s.split(' ')
print(s)
dict={}
for i in s:
dict[i]=s.count(i)
print(dict)
截图：
