How to create timestamp variable in Python?

Question

I am trying to create a timestamp variable which actually stores the present time and outputs the time at that instance. A reproducible code is also included:

import time
from datetime import datetime
t = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
for i in range(5):
    time.sleep(2)
    print t

Output

2015-03-11 11:28:53
2015-03-11 11:28:53
2015-03-11 11:28:53
2015-03-11 11:28:53
2015-03-11 11:28:53

Desired output

2015-03-11 11:28:53
2015-03-11 11:28:55
2015-03-11 11:28:57
2015-03-11 11:28:59
2015-03-11 11:29:01

Any easy way to do this instead of placing the command

datetime.now().strftime('%Y-%m-%d %H:%M:%S')

multiple times in the code.

Why would a string object update itself in a loop? Why not simply use print datetime.now().strftime('%Y-%m-%d %H:%M:%S') in the loop itself? — Martijn Pieters
– Martijn Pieters, Commented Mar 11, 2015 at 12:34
If you want to capture the current time at specific moments, you'll have to call datetime.now() to measure the current time. — Martijn Pieters
– Martijn Pieters, Commented Mar 11, 2015 at 12:35
I have to use it at multiple locations, makes the code look very messy. — Tom Kurushingal
– Tom Kurushingal, Commented Mar 11, 2015 at 12:35
Wouldn't there be a time lag, between the function call and function output? — Tom Kurushingal
– Tom Kurushingal, Commented Mar 11, 2015 at 12:37

Martijn Pieters · Accepted Answer · 2015-03-11 12:37:35Z

4

You cannot avoid having to call datetime.now() if you need to capture the current time at different moments.

Put the call in a function if you feel it is too verbose to repeat:

def current_time():
    return datetime.now().strftime('%Y-%m-%d %H:%M:%S')

then call that:

for i in range(5):
    time.sleep(2)
    print current_time()

answered Mar 11, 2015 at 12:37

Martijn Pieters

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Comments

smalltown2k · Accepted Answer · 2015-03-11 12:35:57Z

0

Move the t=... line into the for loop and/or condense it into the print statement and/or wrap it into a separate function then call that in the for loop.

The latter is going to be a best practice way of doing it if you're going to be using it in other places in the code. It means you only have to change the formatting or time call in a single place in your code.

answered Mar 11, 2015 at 12:35

smalltown2k

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