时间戳字符串（Unix时间）到datetime或pandas.Timestamp

Question

From a source I retrieve some data in JSON format. I want to save this data (measurements in time) as a text file. Repeatedly I want to go the same source and see if new measurements are available, if so I want to add it to the other measurements.

The data I get looks like this:

{"xyz":[{"unixtime":"1458255600","time":"00:00","day":"18\/03","value":"11","paramlabel":"30-500 mHz","popupcorr":"550","iconnr":"7","paramname":"30-500 mHz"},{"unixtime":"1458256200","time":"00:10","day":"18\/03","value":"14","paramlabel":"30-500 mHz","popupcorr":"550","iconnr":"7","paramname":"30-500 mHz"},etc.]}

I load this data into a pandas DataFrame to be able to work with it more easily. When I load this into a dataframe however, all columns are treated as strings. How can I make sure that the unixtime column is treated as a timestamp (such that I can convert to a datetime)?

Answer 1

use to_datetime and pass unit='s' to treat the value as epoch time after converting the dtype to int using astype :

df['unixtime'] = pd.to_datetime(df['unixtime'].astype(int), unit='s')

Example:

In [162]:
pd.to_datetime(1458255600, unit='s')

Out[162]:
Timestamp('2016-03-17 23:00:00')