demo_list=［1,2,3］要求在元素3前面增加元素4最后打印demo_list=［1,2,4,3］用for循环遍历里面的元素输出

好的，关于您的要求，我会进行处理，并且不会透露您的任何信息。以下是您所需要的代码：

demo_list = [1, 2, 3]
demo_list.insert(2, 4)
print(demo_list)
for item in demo_list:
    print(item)

输出结果如下：

[1, 2, 4, 3]
1
2
4
3

希望能够帮助您。

相关问题

定义demo_list=［1,2,3,4,5,6,2,1,3,2］调用count（）统计出列表中某个元素出现的次数比如输入1输出元素次数为：2次

好的，可以这样做：

demo_list = [1, 2, 3, 4, 5, 6, 2, 1, 3, 2]
element = 1
count = demo_list.count(element)
print("元素 {} 出现次数为：{}次".format(element, count))

输出结果为：

元素 1 出现次数为：2次

希望能够帮助您。

import pandas as pd data_demo = [[1,2,3],[4,5,6],[7,8,9]] date_list = [datetime(2020,8,1),datetime(2020,8,1),datetime(2020,8,1)] time_df = pd.DataFra,e(data_demo,index=date_list) print(time_df)

I noticed that there is a typo in your code. Instead of `pd.DataFra,e`, it should be `pd.DataFrame`. Here is the corrected code:

import pandas as pd
from datetime import datetime

data_demo = [[1,2,3],[4,5,6],[7,8,9]]
date_list = [datetime(2020,8,1),datetime(2020,8,1),datetime(2020,8,1)]

time_df = pd.DataFrame(data_demo, index=date_list)
print(time_df)

This code creates a Pandas DataFrame called `time_df` with `data_demo` as the data and `date_list` as the index. The `datetime` module is used to create the `date_list`. Finally, the `print` statement outputs the contents of the `time_df` DataFrame.