timedelta-从字符串传递'days = -5'的最优雅方法

Question

I am trying call a function that triggers a report to be generated with a starting date that is either hour or days ago. The code below works fine but I would like to store the timedelta offset in a mysql database.

starting_date = datetime.today() - timedelta(days=-5)

I had hoped to store 'days=-5' in the database, extract that database column to variable 'delta_offset' and then run

starting_date = datetime.today() - timedelta(delta_offset)

It doesnt like this because delta_offset is a string. I know i could modify the function to just include the offset and store -5 in my database, like what is below. But I really wanted to store days=-5 in the database because my offset can be hours as well. I could make my offset in database always hours and store -120 in the database but was wondering if there was an elegant way where I store 'days=-5' in the database and not cause type issues

starting_date = datetime.today() - timedelta(days=delta_offset)

Answer 1

Instead of storing 'days=-5' in your database as a single column, you could break this into two columns named 'value' and 'unit' or similar. Then you can pass these to timedelta in a dictionary and unpacking. Like so:

unit = 'days'
value = -5
starting_date = datetime.today() - timedelta(**{unit: value})

This will unpack the dictionary so you get the same result as doing timedelta([unit]=value) .

Alternatively, if you really would like to keep 'days=-5' as a value of a single column in your database, you could split the string on '=' then take a similar approach. Here's how:

offset = 'days=-5'
unit, value = offset.split('=')
starting_date = datetime.today() - timedelta(**{unit: int(value)})

Answer 2

i would do it this way:

    date_offset_split = date_offset.split("=")
    kwargs = {date_offset_split[0]: int(date_offset_split[1])}

    starting_date = datetime.today() - timedelta(**kwargs)