作业1 ：
for iin range(1,11):
x =10
x -= i
print('* '* x)
作业2：
a =int(input("请输入一个月份："))
if a ==3 or a ==4 or a ==5:
print("是春季")
elif a ==6 or a ==7 or a ==8:
print("是夏季")
elif a ==9 or a ==10 or a ==11:
print("是秋季")
elif a ==12 or a ==1 or a ==2:
print("是冬季")
作业3:
a =input("请输入一个key:")
d = {'a':'1','b':'2'}
c =list(d.keys())
if ain c:
print("用户key存在")
else:
print("用户key不存在")
