pandas :直接从“日期时间"列返回时间 [英] Pandas: Return Hour from Datetime Column Directly

问题描述

假设我有一个时间戳值的DataFrame sales:

Assume I have a DataFrame sales of timestamp values:

timestamp               sales_office
2014-01-01 09:01:00     Cincinnati
2014-01-01 09:11:00     San Francisco
2014-01-01 15:22:00     Chicago
2014-01-01 19:01:00     Chicago

我想创建一个新列time_hour.我可以这样编写简短函数并使用apply()迭代地应用它来创建它:

I would like to create a new column time_hour. I can create it by writing a short function as so and using apply() to apply it iteratively:

def hr_func(ts):
    return ts.hour

sales['time_hour'] = sales['timestamp'].apply(hr_func)

然后我会看到以下结果:

I would then see this result:

timestamp               sales_office         time_hour
2014-01-01 09:01:00     Cincinnati           9
2014-01-01 09:11:00     San Francisco        9
2014-01-01 15:22:00     Chicago              15
2014-01-01 19:01:00     Chicago              19

我想 要实现的是这样的一些较短的转换(我知道这是错误的，但是很精打细算):

What I'd like to achieve is some shorter transformation like this (which I know is erroneous but gets at the spirit):

sales['time_hour'] = sales['timestamp'].hour

很显然，该列的类型为Series，因此没有这些属性，但似乎有一种使用矩阵运算的简单方法.

Obviously the column is of type Series and as such doesn't have those attributes, but it seems there's a simpler way to make use of matrix operations.

有更直接的方法吗?

推荐答案

假设时间戳是数据帧的索引，则可以执行以下操作:

Assuming timestamp is the index of the data frame, you can just do the following:

hours = sales.index.hour

如果要将其添加到销售数据框中，只需执行以下操作:

If you want to add that to your sales data frame, just do:

import pandas as pd
pd.concat([sales, pd.DataFrame(hours, index=sales.index)], axis = 1)

如果您有几列日期时间对象，则过程相同.如果数据框中有['date']列，并假设'date'具有datetime值，则可以按以下方式访问"date"中的小时:

If you have several columns of datetime objects, it's the same process. If you have a column ['date'] in your data frame, and assuming that 'date' has datetime values, you can access the hour from the 'date' as:

hours = sales['date'].hour

Edit2: 如果要调整数据框中的列，则必须包含dt:

If you want to adjust a column in your data frame you have to include dt:

sales['datehour'] = sales['date'].dt.hour

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