1.假设有20个学生，学分在60～100之间，筛选出成绩在90分以上的学生

import random

stuInfo = {}
for i in range(20):
    name = 'westos' + str(i)
    score = random.randint(60,100)
    stuInfo[name] = score
#     stuInfo['westos'+str(i)] = random.randint(60,100)
hightscore = {}
for name,score in stuInfo.items():
    if score > 90:
        hightscore[name] = score
print hightscore

stuInfo = {'westos'+ str(i):random.randint(60,100) for i in range(20)}
print {name:score for name,score in stuInfo.items() if score >90}

 2.将字典中的key值和value值调换

d = {'a':'apple','b':'bob','c':'cat'}
print {v:k for k,v in d.items()}

d = {'a':'apple','b':'bob','c':'cat'}
print {k:k.upper()for k,v in d.items()}

3.大小写合并，key值最终全部为小写

d1 = {'A':10,'b':3,'a':5,'B':8,'d':1}
print {k.lower():d1.get(k.upper(),0)+d1.get(k.lower(),0)for k,v in d1.items()}