Python 在问答频道中刷题积累到的小技巧（一）

Error = '输入错误，请重新输入!'
while True:
    try:
        n = int(input('请输入一个正整数n(1≤n≤5)：'))
    except:
        print(Error)
        continue
    if 1<=n<=5:
        break
    else:
        print(Error)

Error = '输入错误，请重新输入!'
while True:
    try:
        n = int(input('请输入一个正整数n(0退出)：'))
    except:
        print(Error)
        continue
    if 1<=n<=9:
        for i in range(1,n+1):
            print(f'{(str(i)*(i*2-1)):^{n*2-1}}')
    elif n==0:
        exit(0)
    else:
        print(Error)

>>> 10_000_000 == 10000000
True
>>> 1234_5678_9000 == 123456789000
True

def fib(n, t = False):
    # n:int, n>0; fib->int or list
    if n<3: return [1]*n if t else (n+1)//2
    n1 = n2 = 1
    if t: res = [1,1]
    for i in range(2,n):
        n3 = n1 + n2
        n1,n2 = n2,n3
        if t: res.append(n3)
    if t: return res
    return n3
for i in range(1,11):
    print(i,':',fib(i))
    print(fib(i,True))

def matrixMultiple(A, B):
    res = [[0]*len(B[0]) for _ in range(len(A))]
    for i in range(len(A)):
        for j in range(len(B[0])):
            for k in range(len(A[0])):
                res[i][j] += A[i][k] * B[k][j]
    return res

matrixA = [[1,2],[3,4]]
matrixB = [[5,6],[7,8]]
print(matrixMultiple(matrixA, matrixB))
matrixA = [[1,2,3],[3,2,2],[2,1,2]]
matrixB = [[2,2],[3,1],[2,1]]
print(matrixMultiple(matrixA, matrixB))
matrixA = [[1,2,3],[4,5,6]]
matrixB = [[7,8,9,0],[-1,-2,-3,-4],[5,6,7,8]]
print(matrixMultiple(matrixA, matrixB))
[[19, 22], [43, 50]]
[[14, 7], [16, 10], [11, 7]]
[[20, 22, 24, 16], [53, 58, 63, 28]]
''' 

import random
n = 10
random.seed(n)
lst = [random.randint(-100,100) for _ in range(10)]
print(lst)
# lst = random.choices(range(-100,101), k=10) # 也可但相同种子也与randint()输出随机数不同
lst = sorted(lst, key=lambda x:x if x>=0 else 1/x, reverse=True) # 把负数取倒数实现反序
print(lst)
# 或者升序，但x 1/x取负值一样也降序
random.seed(n)
lst = [random.randint(-100,100) for _ in range(10)]
lst = sorted(lst, key=lambda x:-x if x>=0 else -1/x)
print(lst)
# 或分两段分别排序
random.seed(10)
lst = [random.randint(-100,100) for _ in range(10)]
lst = list(sorted(filter(lambda x:x>=0,lst),reverse=True))+list(sorted(filter(lambda x:x<0,lst)))
print(lst)