Python3.x | 练习集

1、一行解决杨辉三角

def triangles():
    L = [1]
    yield L
    while True:
        L = [1] + [L[i-1] + L[i] for i in range(1, len(L))] + [1]
        yield L
    
n = 0
results = []
for t in triangles():
    results.append(t)
    n += 1
    if n == 10:
        break

for x in results:
    print(x)

>>>
[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]

2、求最大质数值

给定一个n值，求小于等于n的最大的一个质数

from math import sqrt, floor

# 判断是否是质数值，是True，否则False
def is_prime(n):
    if n > 1:
        if n == 2:
            return True
        if n % 2 == 0:
            return False
        for i in range(3, floor(sqrt(n))+1, 2):
            if n % i ==0:
                return False
        return True
    return False

n = int(input())

# 因为求给定值范围内的最大质数，反着依次判断是否为质数，取第一个符合的值即可
while 1:
    if is_prime(n):
        print(n)
        break
    else:
        n -= 1

3、假设没有 float() 方法，把 str 转换成 float 形式

from functools import reduce

d = [str(i) for i in range(10)]
digits = {k:int(k) for k in d}

def prod(num_str):
    # 求出小数部分的长度
    length = len(num_str.split('.')[1])
    
    # 去除'.'
    num_str = num_str.replace('.', '')
    
    num_integer = reduce(lambda x, y: x*10 + y,map(lambda x:digits[x], num_str))
    return num_integer*(10**(-length))

print(prod('789456.123'))

>>>
789456.123

4、输入1000以内的回文（即正反读相同）

def is_palindrome(n):
    if str(n) == str(n)[::-1]:
        return n

L = list(filter(is_palindrome, range(1001)))

print(L)
>>>
[1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484, 494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595, 606, 616, 626, 636, 646, 656, 666, 676, 686, 696, 707, 717, 727, 737, 747, 757, 767, 777, 787, 797, 808, 818, 828, 838, 848, 858, 868, 878, 888, 898, 909, 919, 929, 939, 949, 959, 969, 979, 989, 999]