timedelta - most elegant way to pass 'days=-5' from string

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timedelta - most elegant way to pass 'days=-5' from string



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)





You should probably store the number of seconds in the database (or whatever the smallest unit your offset can be), and then use that to build the timedelta.
– Patrick Haugh
Aug 12 at 1:23


timedelta





Do you realize that you're subtracting a negative offset, thus you're actually getting a later time?
– John Gordon
Aug 12 at 1:23





2 Answers
2



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:


'days=-5'


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).


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:


'days=-5'


'='


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





this is super helpful.
– personalt
Aug 12 at 1:32



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)






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