Python 熊猫：从时间戳中提取日期和时间
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pandas: extract date and time from timestamp
提问by chintan s
I have a timestampcolumn where the timestamp is in the following format
我有一timestamp列时间戳采用以下格式
2016-06-16T21:35:17.098+01:00
I want to extract date and time from it. I have done the following:
我想从中提取日期和时间。我做了以下工作：
import datetime as dt
df['timestamp'] = df['timestamp'].apply(lambda x : pd.to_datetime(str(x)))
df['dates'] = df['timestamp'].dt.date
This worked for a while. But suddenly it does not.
这工作了一段时间。但突然之间就没有了。
If I again do df['dates'] = df['timestamp'].dt.dateI get the following error
如果我再次这样做，df['dates'] = df['timestamp'].dt.date我会收到以下错误
Can only use .dt accessor with datetimelike values
Luckily, I have saved the data frame with datesin the csv but I now want to create another column timein the format 23:00:00.051
幸运的是，我已将数据框保存dates在 csv 中，但我现在想以time该格式创建另一列23:00:00.051
EDIT
编辑
From the raw data file (15 million samples), the timestampcolumn looks like following (first 5 samples):
从原始数据文件（1500 万个样本）中，该timestamp列如下所示（前 5 个样本）：
timestamp
0 2016-06-13T00:00:00.051+01:00
1 2016-06-13T00:00:00.718+01:00
2 2016-06-13T00:00:00.985+01:00
3 2016-06-13T00:00:02.431+01:00
4 2016-06-13T00:00:02.737+01:00
After the following command
执行以下命令后
df['timestamp'] = df['timestamp'].apply(lambda x : pd.to_datetime(str(x)))
the timestampcolumn looks like with dtypeas dtype: datetime64[ns]
该timestamp列看起来像dtypedtype: datetime64[ns]
0 2016-06-12 23:00:00.051
1 2016-06-12 23:00:00.718
2 2016-06-12 23:00:00.985
3 2016-06-12 23:00:02.431
4 2016-06-12 23:00:02.737
Then finally
然后最后
df['dates'] = df['timestamp'].dt.date
0 2016-06-12
1 2016-06-12
2 2016-06-12
3 2016-06-12
4 2016-06-12
EDIT 2
编辑 2
Found the mistake. I had cleaned the data and saved the data frame in a csv file, so I don't have to do the cleaning again. When I read the csv, the timestamp dtypechanges to object. Now how do I fix this?
发现错误。我已经清理了数据并将数据框保存在一个 csv 文件中，所以我不必再次进行清理。当我读取 csv 时，时间戳dtype更改为 object。现在我该如何解决这个问题？
回答by Ajay Goyal
If date is in string form then:
如果日期是字符串形式，则：
import datetime
# this line converts the string object in Timestamp object
df['DateTime'] = [datetime.datetime.strptime(d, "%Y-%m-%d %H:%M") for d in df["DateTime"]]
# extracting date from timestamp
df['Date'] = [datetime.datetime.date(d) for d in df['DateTime']]
# extracting time from timestamp
df['Time'] = [datetime.datetime.time(d) for d in df['DateTime']]
If the object is already in the Timestamp format then skip the first line of code.
如果对象已经是时间戳格式，则跳过第一行代码。
%Y-%m-%d %H:%Mthis means your timestamp object must be in the form like 2016-05-16 12:35:00.
%Y-%m-%d %H:%M这意味着您的时间戳对象必须采用类似 2016-05-16 12:35:00.
回答by Gursel Karacor
Do this first:
先这样做：
df['time'] = pd.to_datetime(df['timestamp'])
Before you do your extraction as usual:
在像往常一样进行提取之前：
df['dates'] = df['time'].dt.date
