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Python Dates and Times in Python (2014) Let's Build a Timed Quiz App Timestamp Ordering

Andrei Oprescu
Andrei Oprescu
9,547 Points
Posted by Andrei Oprescu
Andrei Oprescu
9,547 Points

I am very confused at this task

Hi!

I have stumbled across a challenge that asked me this:

Create a function named timestamp_oldest that takes any number of POSIX timestamp arguments. Return the oldest one as a datetime object.

Remember, POSIX timestamps are floats and lists have a .sort() method.

I don't remember a time where I was thought what a 'POSIX timestamp' is and I don't know how they are written.

can someone tell me what a 'POSIX timestamp' is?

Thanks!

Andrei

timestamp.py 
# If you need help, look up datetime.datetime.fromtimestamp()
# Also, remember that you *will not* know how many timestamps
# are coming in.

3 Answers

John Goodwin
John Goodwin
17,921 Points

This is pretty close! It will actually be easier to use the min() method instead of sort() because of the data. Also, we are missing a classmethod from inside datetime called fromtimestamp. That classmethod will handle the error about integer expected, but got float. The min() method is similar to sorting the data and then taking index 0 (there is also a max() method to get the maximum value).

Code that passes the challenge looks like this:

import datetime
# If you need help, look up datetime.datetime.fromtimestamp()
# Also, remember that you *will not* know how many timestamps
# are coming in
def timestamp_oldest(*args):
    all_timestamps = []
    for value in args:
        all_timestamps.append(value)
    return datetime.datetime.fromtimestamp(min(all_timestamps))

Signed integer is less than minimum is an overflow error. Because the args come in to the function together, you don't actually need to build a list for it. This works as well:

import datetime
def timestamp_oldest(*args):
    return datetime.datetime.fromtimestamp(min(args))
Ross Coe
Ross Coe
5,061 Points
Ross Coe
Ross Coe
5,061 Points

nice and neat

John Goodwin
John Goodwin
17,921 Points
John Goodwin
John Goodwin
17,921 Points

Hi Andrei,

I don't think you need to understand POSIX timestamps to complete the challenge. (Although, POSIX timestamps are basically the time counted in seconds since January 1, 1970, but what's important is they are very large numbers and an earlier timestamp will be a smaller number than a later timestamp.)

For this challenge, this line is important:

Remember, POSIX timestamps are floats and lists have a .sort() method.

All of the timestamps will be in the same format and they will all be floats. If you can get them into a list together and then .sort() the list, you can return the value that is the lowest number.

Andrei Oprescu
Andrei Oprescu
9,547 Points
Andrei Oprescu
Andrei Oprescu
9,547 Points

Hi John!

I have tried to complete the code challenge with this code:

import datetime
# If you need help, look up datetime.datetime.fromtimestamp()
# Also, remember that you *will not* know how many timestamps
# are coming in
def timestamp_oldest(*args):
    all_timestamps = []
    for value in args:
        all_timestamps.append(value)
    all_timestamps.sort()
    return datetime.datetime.date(all_timestamps[-1])

And in return, it gives me this:

descriptor 'date' requires a 'datetime.datetime' object but received a 'float'

Can you tell me what I did wrong in my code and how I can fix it?

Thanks!

John Goodwin
John Goodwin
17,921 Points

Hi Andrei,

I don't think you need datetime.datetime.date in that line. Also, the sort() put the lowest number first and the highest number last, so you may want to check the index you are referencing in the [].

Andrei Oprescu
Andrei Oprescu
9,547 Points
Andrei Oprescu
Andrei Oprescu
9,547 Points

Hi John!

I have done what you said in my code but in the end it said this:

Didn't get back a datetime

I did what it asked me and I came up with this code:

import datetime
# If you need help, look up datetime.datetime.fromtimestamp()
# Also, remember that you *will not* know how many timestamps
# are coming in
def timestamp_oldest(*args):
    all_timestamps = []
    for value in args:
        all_timestamps.append(value)
    all_timestamps.sort()
    result = int(all_timestamps[0])
    return datetime.datetime(year=0, month=0, day=0, hour=0, second=result, microsecond=0)

It then gave me an error saying this:

signed integer is less than minimum

What should I do in this scenario?

Thanks!

Andrei

Andrei Oprescu
Andrei Oprescu
9,547 Points
Andrei Oprescu
Andrei Oprescu
9,547 Points

Oh thanks! I forgot the datetime.fromtimestamp() there. one last thing; is the datetime.fromtimestamp() used to convert a timestamp into a datetime? That's what I understood from that code.

Andrei