Python 100 实例之（21 - 30）

example_021.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 猴子偷桃 '

__author__ = 'Kevin Gong'

peach = 1
for i in range(9):
    peach = (peach + 1) * 2
print(peach)

example_022.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 比赛对手 '

__author__ = 'Kevin Gong'

a = set(['x', 'y', 'z'])
b = set(['x', 'y', 'z'])
c = set(['x', 'y', 'z'])
c -= set(('x', 'z'))
a -= set('x')

for i in a:
    for j in b:
        for k in c:
            if len(set((i, j, k))) == 3:
                print('a:%s,b:%s,c:%s'%(i, j, k))

example_023.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 绘制菱形 '

__author__ = 'Kevin Gong'

def draw(num):
    a = '*' * (2 * (4 - num) + 1)
    print(a.center(9,' '))
    if num != 1:
        draw(num - 1)
        print(a.center(9, ' '))

draw(4)

example_024.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 斐波那契数列Ⅱ '

__author__ = 'Kevin Gong'

a = 2.0
b = 1.0
s = 0
for n in range(1, 21):
    s += a / b
    a, b = a + b, a
print(s)

example_025.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 阶乘求和 '

__author__ = 'Kevin Gong'

res = 1
for i in range(20, 1, -1):
    res = i * res + 1

print(res)

example_026.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 递归求阶乘 '

__author__ = 'Kevin Gong'

def factorial(n):
    if n > 1:
        return n * factorial(n-1)
    else:
        return 1

print(factorial(5))

example_027.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 递归输出 '

__author__ = 'Kevin Gong'

def rec(strs):
    if len(strs) != 1:
        rec(strs[1:])
    print(strs[0],end='')
rec(input('string here: '))

example_028.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 递归求等差数列 '

__author__ = 'Kevin Gong'

def age(n):
    if n == 1:
        return 10
    return 2 + age(n - 1)
print(age(5))

example_029.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 递归求等差数列 '

__author__ = 'Kevin Gong'

n = int(input('输入一个正整数：'))
n = str(n)

print('%d 位数' % len(n))
print(n[::-1])

example_030.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' 回文数 '

__author__ = 'Kevin Gong'

n = input('随便输入：')
a = 0
b = len(n) - 1
flag = True
while a < b:
    if n[a] != n[b]:
        print('不是回文数')
        flag = False
        break
    a , b = a + 1, b - 1
    if flag:
        print('是回文数')