列表理解：將每個字符串乘以一個列表

Question

我有一個字符串列表，並希望得到一個包含在每個元素多次的新列表。

lst = ['abc', '123'] 
n = 3 

我可以做到這一點for循環：

res = [] 
for i in lst: 
    res = res + [i]*n 
print(res) 

['abc', 'abc', 'abc', '123', '123', '123'] 

如何與列表理解做呢？

我最好的嘗試至今：

[ [i]*n for i in ['abc', '123'] ] 
[['abc', 'abc', 'abc'], ['123', '123', '123']] 

Answer 1

使用nested list comprehension

>>> lst = ['abc', '123'] 
>>> n = 3 
>>> [i for i in lst for j in range(n)] 
['abc', 'abc', 'abc', '123', '123', '123'] 

背後的想法是這樣的，你遍歷列表兩次，並在打印單元的每個三次。

見What does "list comprehension" mean? How does it work and how can I use it?

Answer 2

它也可以做到：

>>> lst = ['abc', '123'] 
>>> n=3 
>>> [j for i in lst for j in (i,)*n] 
['abc', 'abc', 'abc', '123', '123', '123']