(二)2-4练习小结

1、实现1-100的所有的和

sum = 0
for i in range(101):
    sum +=i
print(sum)

运行结果：

5050

 2、实现1-500所有奇数的和

sum = 0
for i in range(1,501,2):
    sum +=i
print(sum)

运行结果：

62500

3、求1+ 2! + 3! + 4! + ……20！的和

def myfact(n):
    if n < 0:
        print("负数没有阶乘！！！")
    elif n <2 :
        return  1
    else :
        return  n * myfact(n-1)
def get_sum(m):
    sum = 0
    for i in range(1,m+1):
        sum  += myfact(i)
    return  sum
print(get_sum(20))

运行结果：

2561327494111820313

4、对指定一个list进行排序[2,32,43,453,54,6,576,5,7,6,8,78,7,89]

list1 = [2,32,43,453,54,6,576,5,7,6,8,78,7,89]
print(type(list1))
list1.sort(reverse=False)
print(list1)
list2 = [2,32,43,453,54,6,576,5,7,6,8,78,7,89]
list2.sort(reverse=True)
print(list2)
print('*'*30)

运行结果：

<type 'list'>
[2, 5, 6, 6, 7, 7, 8, 32, 43, 54, 78, 89, 453, 576]
[576, 453, 89, 78, 54, 43, 32, 8, 7, 7, 6, 6, 5, 2]

5、字典排序

dic = {"d":87,"a":54,"c":15,"b":99,"e":66}
#按字典键排序
a = sorted(dic.items(),key=lambda x:x[1],reverse=False)
print(a)
#按字典值排序
a = sorted(dic.items(),key=lambda x:x[0],reverse=False)
print(a)

运行结果：

[('c', 15), ('a', 54), ('e', 66), ('d', 87), ('b', 99)]
[('a', 54), ('b', 99), ('c', 15), ('d', 87), ('e', 66)]