从用户输入检查列表中的重复项

Question

所以我编写了一个代码，它生成一个随机值的随机列表。然后询问用户用户正在寻找什么号码，如果它在列表中，它会告诉用户该号码在列表中的哪个位置。

import random

a = [random.randint(1, 20) for i in range(random.randint(8, 30))]

a.sort()
print(a)


def askUser():

    n = input("What number are you looking for?")
    while not n.isdigit():
        n = input("What number are you looking for?")

    n = int(n)
    s = 0

    for numbers in a:
        if numbers == n:
            s += 1
            print("Number", n, "is located in the list and the position is:", (a.index(n)+1))
            # Something here to skip this index next time it goes through the loop
        else:
            pass
    if s == 0:
        print("Your number could not be found")


askUser()

我想添加一些内容，它会跳过第一次找到的索引，然后查找重复的索引（如果有的话）。

当前结果

[2, 4, 8, 9, 10, 10, 16, 19, 20, 20]
What number are you looking for?20
Number 20 is located in the list and the position is: 9
Number 20 is located in the list and the position is: 9

想要的结果

[2, 4, 8, 9, 10, 10, 16, 19, 20, 20]
What number are you looking for?20
Number 20 is located in the list and the position is: 9
Number 20 is located in the list and the position is: 10

Answer 1

改变这一行：

for numbers in a:

收件人：

for i, numbers in enumerate(a):

然后更改打印索引的方式：

print("Number", n, "is located in the list and the position is:", (i+1))

样本输出：

[1, 2, 2, 5, 5, 5, 6, 7, 8, 8, 8, 10, 10, 10, 10, 10, 11, 11, 16, 17, 17, 19, 19]
What number are you looking for? 8
Number 8 is located in the list and the position is: 9
Number 8 is located in the list and the position is: 10
Number 8 is located in the list and the position is: 11

Answer 2

如果您喜欢，可以将一些循环转换为列表推导：

def askUser():

    n = input("What number are you looking for?")
    while not n.isdigit():
        n = input("What number are you looking for?")

    n = int(n)

    # get a list of all indexes that match the number
    foundAt = [p+1 for p,num in enumerate(a) if num == n]

    if foundAt:
        # print text by creating a list of texts to print and decompose them
        # printing with a seperator of linefeed
        print( *[f"Number {n} is located in the list and the position is: {q}" for 
                 q in foundAt], sep="\n")
    else: 
        print("Your number could not be found")

编辑：正如 Chrisz 指出的那样，f"" 格式字符串随附于 Python 3.6 的 PEP-498（不知道 :o/ ） - 所以对于早期的 3.x，Python 必须使用

print( *["Number {} is located in the list and the position is: {}".format(n,q) for 
                 q in foundAt], sep="\n")

Answer 3

您可以使用numpy 简化此代码以删除您的循环。

a = np.array([random.randint(1,20) for i in range(random.randint(8,30))])

然后您可以使用np.where 来确定用户是否在您的随机值数组a 中选择了一个值：

idx_selections = np.where(a == n)[0]

然后您可以处理用户是否匹配答案：

if len(idx_selections) == 0:
    print("Your number could not be found")
else:
    for i in idx_selections:
        print("Number", n, "is located in the list and the position is:", i)

Answer 4

num =20

numlist = [2, 4, 8, 9, 10, 10, 16, 19, 20, 20]

for each in numlist:
    if num is each:
        print num
        print [i for i, x in enumerate(numlist) if x == num]