Python：如何將for循環的結果合併爲一個輸出？

Question

numbers = [1, 2, 3] 

for number in numbers: 
    number = number * 2 

#For the output I will get: 
2 
4 
6 

如何在不使用打印語句的情況下修改我的代碼，使結果可以結合起來（如[2，4，6]）？

Answer 1

使用列表理解：

[num*2 for num in numbers] 

---

>>> numbers = [1, 2, 3] 
>>> [num*2 for num in numbers] 
[2, 4, 6] 
>>> 

Answer 2

創建新列表類型的變量result和列表append()方法添加值到它。

演示：

>>> numbers = [1, 2, 3] 
>>> result = [] 
>>> for i in numbers: 
... result.append(i*2) 
... 
>>> result 
[2, 4, 6] 
>>> 

Answer 3

如果你想收集結果到一個列表中，您只需創建一個列表，並append每一個到它：

numbers = [1, 2, 3] 
doubles = [] 
for number in numbers: 
    double = number * 2 
    doubles.append(double) 

...或者，更緊湊，做與列表理解相同：

numbers = [1, 2, 3] 
doubles = [number * 2 for number in numbers]