2-12 字典练习

写代码，由如下字典，按照要求实现每一个功能 dic = {'k1':'v1','k2':'v2','k3':'v3'}

1.请循环遍历出所有的key

for key in dic:
    print(key)

2.请循环遍历出所有的value

for key in dic:
    print(dic[key])

3.请循环遍历出所有的key 和 value

for key in dic:
    print(key,dic[key])

4.请在字典中添加一个键值对，‘k4':'v4'，输出添加后的字典

dic['k4'] = 'v4'

for key in dic:
    print('%s:%s'%(key,dic[key]),end = ' ')

5.请删除字典中键值对‘k1’:'v1'，并输出删除后的字典

>>> dic.pop('k1')
'v1'
>>> dic
{'k2': 'v2', 'k3': 'v3', 'k4': 'v4'}

6.请删除字典中的键‘k5’对应的键值对，如果字典中不存在键‘k5’,则不报错，返回None

if dic.get('k5') != None:
   dic.pop('k5')

7.请获取字典中'k2'对应的值

>>> dic = {'k1':'v1','k2':'v2','k3':'v3','k4':'v4','k5':'v5'}
>>>
>>> dic.get('k2')
'v2'

8.现有dic2 = {'k1':'v111','a':'b'}通过一行操作使dic2 = {'k1':'v1','k2':'v2','k3':'v3','a':'b'}

>>> dic2 = {'k1':'v111','a':'b'}
>>> dic2.update({'k1':'v1','k2':'v2','k3':'v3'})
>>> dic2
{'k1': 'v1', 'a': 'b', 'k2': 'v2', 'k3': 'v3'}