CODEWITHSUNDEEP
pythonstring-formatting
JL Peyret
JL Peyret

Reputation: 12154

How do I drop leftmost digits from a float?

I was trying to print out sub-seconds timing in a bash shell, using Python.

This is somewhat related to how-to-get-execution-time-of-a-script-effectively. I'm on macos and bash provides no subsecond timings there.

If I use python -c 'from time import time; print(f"{time():.3f}")' for example I get:

1603052253.465

python -c 'from time import time; print(f"{time():4.3f}")' has the same output behavior.

Now, this quite noisy. I don't really need to see all the leftmost digits to eyeball execution time from step to step.

I wrote a new script that does it much more nicely:

$ time4bash.py

 2325.987

$ time4bash.py

 2328.201

But the code to do it was somewhat more involved than I would have preferred.

from time import time
time_ = time()
stime = f"{time_:.3f}"

#look for decimal separator, and this will break on `,` locales
pos = stime.index(".")
tstime = stime[pos-4:]

print(tstime)

Is there a better way using either string format flags or modulo math?

Upvotes: 1

Views: 185

Answers (2)

Joe Ferndz
Joe Ferndz

Reputation: 8508

If you want to convert time to hour, min, secs only, you can try something like this.

time.strftime("%H:%M:%S", time.gmtime())

This will return:

'20:42:13'

You can also get local time using:

time.strftime("%H:%M:%S", time.localtime())

This will return:

'13:47:54'

Upvotes: -1

ShadowRanger
ShadowRanger

Reputation: 155363

Just compute the remainder modulo 10,000 before formatting it with .3f:

>>> t = time.time()
>>> t
1603052957.262341

>>> t % 10000
2957.2623410224915

>>> '{:.3f}'.format(t % 10000)
'2957.262'

or put all together in one line:

print('{:.3f}'.format(time.time() % 10000))

Upvotes: 3

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