英文:
Replacing two items with one item in a list
问题
如何在Python中用单个元素替换列表中的两个元素？
例如：
list_a = [1, 2, 3, 4, 5, 6, 7]
如果我想用9替换2和3，我只知道它们的索引（我不知道值）
list_a = [1, 9, 4, 5, 6, 7]
英文:
How to replace two elements in a list with single element in Python?
For example:
list_a = [1, 2, 3, 4, 5, 6, 7]
if I wanted to replace 2 and 3 with let's say 9 and I only know the indices, (I don't know the values)
list_a = [1, 9, 4, 5, 6, 7]
答案1
得分: 9
在Python中，你可以使用切片并将值分配给列表：
list_a = [1, 2, 3, 4, 5, 6, 7]
list_a[1:3] = [9] # list_a[1:3] 表示元素 [2, 3]
print(list_a)
输出结果：[1, 9, 4, 5, 6, 7]
请注意，在Python中索引从 0 开始，因此你的切片是 1:3（索引从1到3，不包括3），更多细节请参考Python中切片的工作原理。
# 索引: 0 1 2 3 4 5 6
list_a = [1, 2, 3, 4, 5, 6, 7]
# 切片: x x
英文:
IIUC, you could use a slice and assign your value as list:
list_a = [1, 2, 3, 4, 5, 6, 7]
list_a[1:3] = [9] # list_a[1:3] are elements [2, 3]
print(list_a)
Output: [1, 9, 4, 5, 6, 7]
Note that in python the indices start with 0, thus your slice is 1:3 (indices 1 to 3, excluding 3), see How slicing in Python works for more details.
# indices: 0 1 2 3 4 5 6
list_a = [1, 2, 3, 4, 5, 6, 7]
# slice: x x
答案2
得分: 0
我们可以使用列表切片方法：
list_a = [1, 2, 3, 4, 5, 6, 7]
# 这里你想要消除第 2 和 3 个元素，然后用 9 替换它们
index = list_a.index(2)
# 语法：l = l[:index] + ['new_value'] + l[index+2:]
list_a = list_a[:index] + [9] + list_a[index+2:]
print(list_a)
输出：
[1, 9, 4, 5, 6, 7]
英文:
we can use the list slicing method
list_a = [1, 2, 3, 4, 5, 6, 7]
# here you want to eliminate 2,3 elements and replace 9 instead of them
index= list_a.index(2)
# Syntax: l=l[:index]+[‘new_value’]+l[index+2:]
list_a = list_a[ :index] + [9] + list_a[index+2: ]
print(list_a)
Output:
[1, 9, 4, 5, 6, 7]
答案3
得分: 0
你可以使用列表切片来解决你的问题。示例代码：
# 创建你的列表
list_a = [1, 2, 3, 4, 5, 6, 7]
# 将索引1到3的元素，即第2到第4个元素替换为9
list_a[1:3] = [9]
然后你可以打印列表：
print(list_a)
输出结果：
[1, 9, 4, 5, 6, 7]
请注意，你必须将9放在方括号内。这是因为你只能用可迭代对象替换多个元素。所以，将九放在方括号内，使它成为可迭代对象。不将9放在方括号内将导致TypeError错误。
英文:
You can use list slices to solve your problem. Example code:
#Create your list
list_a = [1, 2, 3, 4, 5, 6, 7]
#Replace the elements from index 1 to 3 i.e. 2nd to 4th element with 9
list_a[1:3] = [9]
Then you can print the list:
print(list_a)
Output:
[1, 9, 4, 5, 6, 7]
Note that you have to put 9 within square brackets. This is because you can replace multiple elements only with an iterable. So, putting nine within square brackets, makes it an iterable object. Not putting 9 within brackets will give a TypeError.
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