Python列表将特定元素限制为N次

Question

我有一个列表，里面有7个项目，比如['S1','S1','S1','S1','L','L','L']，我想将'L'限制为2次，其余的限制为'S1'。

Answer 1

使用计数器统计列表中Lelem的出现次数，并相应地追加：

s = ['S1','S1','S1','S1','L','L','L']
c = 0
res = []
for el in s:
if el != 'L':
res.append(el)
elif c < 2:
c += 1
res.append(el)   
print(res)

输出：

['S1', 'S1', 'S1', 'S1', 'L', 'L']

编辑：

如果要将L的其余部分替换为S1:

s = ['S1','S1','S1','S1','L','L','L']
c = 0
res = []
for el in s:
if el != 'L':
res.append(el)
else:
if c < 2:
c += 1
res.append(el)
else:
res.append("S1")
print(res)

输出：

['S1', 'S1', 'S1', 'S1', 'L', 'L', 'S1']

Answer 2

试试看：

lst = ["S1","S1","S1","S1","L","L","L"]
limit = 2
value = "L"
new_lst = []
counter = 0
for i in lst:
if counter == limit and i == value:
continue
if i == value:
counter += 1
new_lst.append(i)
print(new_lst)