python - 计算列表中相邻重复元素的数量

Question

我的期望:

input = ["a", "a", "a", "c", "b", "b", "c"]
output: ['a', '3', 'c', '1', 'b', '2', 'c', '1']

我的代码:

lst = ["a", "a", "a", "c", "b", "b", "c"]

result = []
index = 0

while(index < len(lst)-1):
    count = 1
    result.append(lst[index])
    while(lst[index] == lst[index+1]):
        count += 1
        index += 1

    result.append(str(count))
    index += 1
    print("step: ", result)

print("result: ", result) 

我得到了什么:

step:  ['a', '3']
step:  ['a', '3', 'c', '1']
step:  ['a', '3', 'c', '1', 'b', '2']
result:  ['a', '3', 'c', '1', 'b', '2']

我无法正确计算最后一个元素。

这是另一个输入:

['East', 'East', 'East', 'East', 'East', 'West', 'West', 'West', 'West', 'North', 'South', 'West', 'West', 'West', 'North', 'South', 'West', 'West', 'West', 'North', 'North', 'West', 'West', 'West', 'East', 'East', 'East', 'East', 'East', 'East', 'East', 'East', 'East', 'East', 'East', 'East', 'South', 'South', 'East', 'East', 'East', 'North', 'North', 'East', 'East', 'South', 'South', 'South', 'South', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West', 'West']

Answer 1

您的代码未考虑列表中的最后一项，因为您要避免在评估lst[index] == lst[index+1]时出现索引越界错误。通过使用 while(index < len(lst)-1): 迭代比列表长度小 1 的范围.

一个无需在循环后重复计数代码的简单解决方法是首先无条件地将虚拟项附加到列表中，如果您仍然需要完整的原始列表，则可以选择在计数完成后弹出它。下面的示例使用 object 的实例作为虚拟项目，因为它有助于确保 lst[index] == lst[index+1] 的最后评估永远不会是True :

lst.append(object()) # append a dummy item first
while(index < len(lst)-1):
    count = 1
    result.append(lst[index])
    while(lst[index] == lst[index+1]):
        count += 1
        index += 1

    result.append(str(count))
    index += 1
    print("step: ", result)

lst.pop() # add this line only if you still need the original lst for later use