Subtracting tuple from tuple?

9 minutes into this video, the lady suggests subtracting date.time(today) with date.time(date of birth) in order to get a person’s age -

It doesn’t make sense, because it doesn’t list it over here as one of the possible tuple operations:


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That doesn’t look like a tuple operation, but a value operation. The result will likely be a normalization of subtracting two timestamps. That’s not a certainty, and if we have a link to the exercise we can delve further into this. Please post the URL.

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Somewhere in the video, it shows the code that they’re working with; I think around 9 minutes in

It actually starts with a string for birthday, then splits it and converts it to integers. But then (to me at least) it puts those integers into a tuple later, and then subtracts it from another tuple.

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Please relate this to a lesson, or furnish us with some real code to test. Videos are not really my thing, if you are willing to forgive me that.

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class User:
  def __init__(self, full_name, birthday): = full_name
    self.birthday = birthday

    #extract first and last names
    name_pieces = full_name.split(" ")
    self.first_name = name_pieces[0]
    self.last_name = name_pieces[-1]

  def age(self):
    '''Return age of user in years'''
    today =, 5, 12)
    yyyy = int(self.birthday[0:4])
    mm = int(self.birthday[4:6]
    dd = int(self.birthday[6:8])
    dob =, mm, dd) 
    age_in_days = (today - dob).days
    age_in_years = age_in_days/365
    return int(age_in_years)

user = User("Dave Bowman", "19710315")

I haven’t tested this code (gotta go to bed soon), but I don’t understand why they’re able to do math like that with tuples.

And if they aren’t tuples, can you explain to me why not?

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As mentioned earlier, the tuples are normalized timestamps . Timestamps are numbers.

The datetime object has special methods at its disposal for resolving timestamps into normalized dates and vice-versa.

February 23, 2019

How would we get that into a timestamp?

>>> import datetime
>>> now =
>>> now.timestamp()
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Still, the other hard coded value is a tuple, isn’t it?


Wonder why that’s the result?

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The return value from the timestamp method is a float. It is a running count of some unit of time starting around January 1st, 1970.

>>> from datetime import datetime
>>> a = datetime(1970, 1, 1)
>>> a.timestamp()
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Oh so I can set any 3 item tuple to datetime and have it be treated as a float?

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That is not a tuple, but an argument list (year, month, day). Don’t be getting these confused. Just because we see parens does not make it a tuple.

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So it’s a sequence???

In that a sequence is a type of list, yes, but it is not a sequence in the classic sense since the terms have no relationship to each other.