python练习（1）

た入场券 2022-12-29 14:12 52阅读 0赞

python学习（1）- 变量

"""
    1.杨辉三角
        [1],
        [1, 1],
        [1, 2, 1],
        [1, 3, 3, 1],
        [1, 4, 6, 4, 1],
        [1, 5, 10, 10, 5, 1],
        [1, 6, 15, 20, 15, 6, 1],
        [1, 7, 21, 35, 35, 21, 7, 1],
        [1, 8, 28, 56, 70, 56, 28, 8, 1],
        [1, 9, 36, 84, 126, 126, 84, 36, 9, 1]
    """
    
    
    def triangles():
        L = [1]
        while True:
            yield L
            L = [1] + [L[n] + L[n + 1] for n in range(len(L) - 1)] + [1]
    
    
    n = 0
    results = []
    for t in triangles():
        results.append(t)
        n = n + 1
        if n == 5:
            break
    for t in results:
        print(t)
    
    """
    2.请修改列表生成式，通过添加if语句保证列表生成式能正确地执行：
    """
    L1 = ['Hello', 'World', 18, 'Apple', None]
    # L2 = []
    # for i in L1:
    #     if isinstance(i, str):
    #         L2.append(i.lower())
    L2 = [i.lower() for i in L1 if isinstance(i, str)]
    # 测试:
    print('L2:', L2)
    if L2 == ['hello', 'world', 'apple']:
        print('测试通过!')
    else:
        print('测试失败!')
    
    """
    3.斐波那契数列
        1 1 2 3 5 8 13 21 34 。。。
    """
    
    
    def fib(num):
        i, a, b = 0, 0, 1
        while i < num:
            yield b
            a, b = b, a + b
            i += 1
    
    
    for i in fib(5):
        print(i)
    
    """
    4.小明的成绩从去年的72分提升到了今年的85分，
      请计算小明成绩提升的百分点，
      并用字符串格式化显示出'xx.x%'，只保留小数点后1位：
    
    """
    s1 = 72
    s2 = 85
    r = (s2 - s1) / s1 * 100
    print('百分点{0:.1f}%'.format(r))
    
    """
    5.元组的’修改是否正确‘ 为什么
    """
    l5 = ['A', 'B']
    t5 = ('a', 'b', l5)
    t5[2][0] = 'C'
    print(t5)  # ('a', 'b', ['C', 'B'])
    # 可以的 l5的内存地址是没有修改的  元素指向没有变

python练习（2）