循环

while

for

计算阶乘：

程序示例：

# 阶乘
n = input("Enter a number: ")
if n.isdigit():
    n = int(n)
    factorial = 1
    for i in range(1, n + 1):
        factorial = factorial * i
    print("The factorial of {} is {}".format(n, factorial))
else:
    print("Enter a number")

结果：

Enter a number: 3
The factorial of 3 is 6

计算 1! + 2! + 3! + ... + n!

程序示例：

n = input("Enter a number: ")
if n.isdigit():
    n = int(n)
    result = 0
    for i in range(1, n + 1):
        factorial = 1
        for j in range(1, i + 1):
            factorial = j * factorial
        print("%d 的阶乘为：%d" % (i, factorial))
        result = result + factorial
    print("%d 的计算结果为：%d" % (n, result))
else:
    print("Enter a number")

结果：

Enter a number: 3
1 的阶乘为：1
2 的阶乘为：2
3 的阶乘为：6
3 的计算结果为：9

break

判断是否为质数：

程序示例：

num = input("Enter a number: ")
if num.isdigit():
    num = int(num)
    for i in range(2, num):
        if i * i > num:
            print(num, "is a prime number")
            break
        else:
            if num % i == 0:
                print(num, "is not a prime number")
                break
else:
    print("Enter a number")

else 可以跟在 while 或 for 循环后面，表示 while 里面的 if 里面的 break 没有执行时，将执行 else 里的语句。如果 break 被执行了，则 else 内的语句不会被执行。

程序示例：

num = input("Enter a number: ")
if num.isdigit():
    num = int(num)
    a = 2
    while a < num:
        if num % a == 0:
            print(num, "is not a prime number")
            break
        a = a + 1
    else:
        print(num, "is a prime number")
else:
    print("Enter a number")

程序示例：

num = input("Enter a number: ")
if num.isdigit():
    num = int(num)
    for i in range(2, num):
        if num % i == 0:
            print(num, "is not a prime number")
            break
    else:
        print(num, "is a prime number")
else:
    print("Enter a number")

continue

pass

作用：当语句要求不希望任何命令或代码来执行时使用。

说明：pass 语句表示一个空操作，在执行时没有任何的响应，pass 的位置最终应该有代码来执行，只不过暂时写不出来。

pass 语句可以在流程控制和循环语句中使用。

程序示例：

if 1:
    pass

while 1:
    pass

杨辉三角形：

程序示例：

n = 8
for i in range(1, n + 1):
    print(' ' * (n - i), end='')
    print('*' * (2 * i - 1))

九九乘法表：

程序示例：

row = 1
col = 1
for row in range(1, 10):
    for col in range(1, row + 1):
        print("%d x %d = %d" % (col, row, row * col), end="  ")
    print()

结果：

1 x 1 = 1  
1 x 2 = 2  2 x 2 = 4  
1 x 3 = 3  2 x 3 = 6  3 x 3 = 9  
1 x 4 = 4  2 x 4 = 8  3 x 4 = 12  4 x 4 = 16  
1 x 5 = 5  2 x 5 = 10  3 x 5 = 15  4 x 5 = 20  5 x 5 = 25  
1 x 6 = 6  2 x 6 = 12  3 x 6 = 18  4 x 6 = 24  5 x 6 = 30  6 x 6 = 36  
1 x 7 = 7  2 x 7 = 14  3 x 7 = 21  4 x 7 = 28  5 x 7 = 35  6 x 7 = 42  7 x 7 = 49  
1 x 8 = 8  2 x 8 = 16  3 x 8 = 24  4 x 8 = 32  5 x 8 = 40  6 x 8 = 48  7 x 8 = 56  8 x 8 = 64  
1 x 9 = 9  2 x 9 = 18  3 x 9 = 27  4 x 9 = 36  5 x 9 = 45  6 x 9 = 54  7 x 9 = 63  8 x 9 = 72  9 x 9 = 81