01月23日【Python3 基础知识】

'''
#
if 判断条件：
    执行语句
elif 判断条件：
    执行语句
else:
    执行语句
#
while 判断条件：
    执行语句
# 
break: 跳出循环
#
continue: 跳出当次循环
#
for item in sequence:
    执行语句
'''
# lsit 遍历
l = ['a', 'b', 'c', 'd', 'e']
for x, y in enumerate(l):
    print(x, y)

# ABCD * 9 = DBCA  答案：A=1 B=0 C=8 D=9
for A in range(1, 10):
    for B in range(0, 10):
        for C in range(0, 10):
            for D in range(1, 10):
                start = 1000 * A + 100 * B + 10 * C + D
                end = 1000 * D + 100 * C + 10 * B + A
                if start * 9 == end:
                    print("A={0};B={1};C={2};D={3}".format(A, B, C, D))
                    print("{0} * 9 = {1}".format(start, end))

# 阶乘相加
def one(n):
    total = 1
    if n == 0:
        total = 1
    else:
        for i in range(1, n+1):
            total *= i
    return total
result = 0
n = int(input("输入<=0的数字："))
for i in range(0, n+1):
    result += one(i)
print(result)