在Python中将sqlite3时间戳转换为纪元时间

Question

I would like to convert the datetime I select from my sqlite3 database into unixepoch. An easy way would be, I guess, to insert timestamps in my database in unixepoch, but I would rather not, since it makes my database less readable.

conn = sqlite3.connect('test.db')
c = conn.cursor() 
c.execute('CREATE TABLE if not exists table_name (datetime text, column1 real, column2 real)')
cur.execute("INSERT INTO table_name VALUES (datetime(CURRENT_TIMESTAMP, 'localtime'),?,?)", data)
c.execute("SELECT datetime from table_name")

#here I would like to convert the above selection (datetime in localtime) to unixepoch

Thank you for reading this!

Answer 1

The sqlite3 database already comes with an adapter to interpret ISO date-time formats as datetime.datetime() objects :

c.execute('SELECT datetime as "datetime [timestamp]" from table_name')
for datetime, in c:
    print type(datetime)

This will print <type 'datetime.datetime'> for each row. datetime.datetime() objects are far more flexible and powerful than UNIX epoch offsets.

Note the as "datetime [timestamp]" alias; this adds type information to the column overriding the text type for that column in the CREATE TABLE definition, allowing Python to apply the type adapter. If you declare your column as timestamp you don't even have to make your query use an alias:

c.execute('CREATE TABLE if not exists table_name (datetime timestamp, column1 real, column2 real)')

If you have to use UNIX epoch offsets, you can convert them with the time.mktime() function and the datetime.datetime.timetuple() method :

timeoffset = time.mktime(datetime.timetuple())