Cross platform Python code

Question

EDIT

Further to the other below info and thanks to some helpful input the issue is caused by using strftime %s to generate a Unix Timestamp (which is what the system being queried requires). Strftime %s is not compatible with the Windows platform therefore I need to use an alternative method to generate the Unix Timestamp. Jez has suggested time.time() which I have experimented with but I'm clearly not doing it right somewhere along the way. I need to change this section of code from using strftime to time():

    if (args.startdate):
       from_time=str(int(args.startdate.strftime('%s')) * 1000)
    if (args.enddate):
       to_time=str(int(args.enddate.strftime('%s')) * 1000)

Any help or a steer greatly appreciated. :)

/EDIT

I've been given a Python script which appears to run ok when deployed on an Apple laptop but gives an error message when I run it on a Windows machine. I need to talk a 3rd party through executing the file remotely and he only has a windows machine so I need to try and figure out why it isn't working. I'm running 2.7 for reference. This section appears to be where the error is being caused:

if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.add_argument('-s', "--startdate", help="The start date (included)- format YYYY-MM-DD -- if not specified then earliest available data", type=valid_date)
parser.add_argument('-e', "--enddate", help="The end date (excluded) - format YYYY-MM-DD  -- if not specified then 'now'", type=valid_date)
parser.add_argument('-u', "--user", help="User name to use", default='admin')
parser.add_argument('-p', "--password", help="Password for user", default='redwood')
parser.add_argument('-a', "--attribute", help="Attribute", choices=['temperature', 'motion', 'input-power', 'output-power'], default='motion')
parser.add_argument('host', help='Hostname/IP address of engine to connect to', default='127.0.0.1')
args = parser.parse_args()
    user = args.user    
    passwd = args.password
    if (args.startdate):
       from_time=str(int(args.startdate.strftime('%s')) * 1000)
    if (args.enddate):
       to_time=str(int(args.enddate.strftime('%s')) * 1000)

    scale=1
    unit='seconds since 1.1.1970'
    if (args.attribute == 'temperature'):
       path=temperature_path
       scale = 100
       unit = "Degrees Celsius"
    elif (args.attribute == 'output-power'):
       path=opower_path
       scale = 100
       unit = "Watts"
    elif (args.attribute == 'input-power'):
       path=ipower_path
       scale = 1000
       unit = "Watts"
    else:
       path=motion_path
    print "Epoch Time, Local Time (this machine), Attribute, Value (%s) " % unit
query_stats(args.host)

This is the command I'm using to execute:

C:\Python27>python stats_query.py -s 2016-03-18 -e 2016-03-19 -u admin -p admin -a motion 192.168.2.222

And this is the error message I get:

Traceback (most recent call last):
File "stats_query.py", line 132, in <module>
from_time=str(int(args.startdate.strftime('%s')) * 1000)
ValueError: Invalid format string

If anyone has any thoughts I'd greatly appreciate any feedback. Apologies if I'm asking a stupid question - I'm really not very familiar with Python.

possible duplicate of stackoverflow.com/questions/10807164/… — zoubida13
– zoubida13, Commented May 9, 2016 at 13:51
Be cautious using the solutions offered here: yes, changing to '%S' will make the code run without an exception, but your from_time will then only ever be a number from 0 to 59 (the "seconds" part of a formatted time). That's fairly useless as a baseline from which to measure elapsed time, because of wraparounds. You may simply want time.time() instead of anything to do with strftime — jez
– jez, Commented May 9, 2016 at 14:18
Thanks Jez, You're exactly right. Having done some more research the complete list of arguments shows %S and %s are entirely different functions. Basically the system is using unix time and it appears that windows doesn't support the %s argument which specifically relates to the unix time epoch. The manual states: %s Unix Epoch Time timestamp (same as the time() function) Am I correct in assuming that I should be able to utilise the time() function as an alternative? — Robin S
– Robin S, Commented May 10, 2016 at 13:44
I have changed to this but still get an error back/; if (args.startdate): from_time=str(int(args.startdate.time.time) * 1000) if (args.enddate): to_time=str(int(args.enddate.time.time) * 1000) — Robin S
– Robin S, Commented May 10, 2016 at 19:20

ForceBru · Accepted Answer · 2016-05-09 13:51:05Z

1

If you want to print this in seconds, use %S (with a capital S).

answered May 9, 2016 at 13:51

ForceBru

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1 Comment

Robin S Over a year ago

I did try this but I got a different response which didn't help either so I changed it back again. It simply responded with: Epoch Time, Local Time (this machine), Attribute, Value (seconds since 1.1.1970)

DeepSpace · Accepted Answer · 2016-05-09 14:02:56Z

0

(Should maybe be a comment)

As others have mentioned already, not all directives are available on all platforms.

Python's documentation lists all directives which are cross-platform: https://docs.python.org/2/library/datetime.html#strftime-strptime-behavior

answered May 9, 2016 at 14:02

DeepSpace

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5 Comments

Robin S Over a year ago

OK Thanks, I did check this stuff previously and %S does appear to be in the list of cross platform directives so I'm not sure what I'm looking for here?

DeepSpace Over a year ago

%S (upper case S) is on this list, but your code uses %s (smaller case s)

Robin S Over a year ago

Ok something that has jumped out at me is this: Because the format depends on the current locale, care should be taken when making assumptions about the output value. Field orderings will vary (for example, “month/day/year” versus “day/month/year”) This was written by a guy in the states and I'm in the UK so is it possible that the date format will be different based on my PC's settings?

DeepSpace Over a year ago

@RobinS Not in this case. %S will always output the seconds, as %m will always output the month.

Robin S Over a year ago

I'm wondering if the error is with the 'startdate' variable rather than the '%s'? If I leave out the date range in my command line it works correctly - i.e. it drops 2 years worth of data out. When I add the start and end date it gives the error message.

GNewc · Accepted Answer · 2016-05-17 16:30:10Z

0

Not sure what valid_time is in your function, but if you use something like:

def valid_time(t):
    format = "%Y-%m-%d"
    datetime.datetime.strptime(t, format)

It gets past the issue you are describing... after that, I see other issues, since motion_path is not defined.

UPDATE: The following code works running on Windows7 Professional using python 2.7 (file saved as tryme.py)

import argparse
import datetime

def motion_path():
  print "Got here.. no issues"

def query_stats(host):
  print "We'll query the host: %s" % host

def valid_time(t):
  format = "%Y-%m-%d"
  return datetime.datetime.strptime(t, format)

if __name__ == "__main__":
  parser = argparse.ArgumentParser()
  parser.add_argument('-s', "--startdate", help="The start date (included)- format YYYY-MM-DD -- if not specified then earliest available data", type=valid_time)
  parser.add_argument('-e', "--enddate", help="The end date (excluded) - format YYYY-MM-DD  -- if not specified then 'now'", type=valid_time)
  parser.add_argument('-u', "--user", help="User name to use", default='admin')
  parser.add_argument('-p', "--password", help="Password for user", default='redwood')
  parser.add_argument('-a', "--attribute", help="Attribute", choices=['temperature', 'motion', 'input-power', 'output-power'], default='motion')
  parser.add_argument('host', help='Hostname/IP address of engine to connect to', default='127.0.0.1')
  args = parser.parse_args()
  user = args.user  
  epoch = datetime.datetime.utcfromtimestamp(0)
  passwd = args.password
  if (args.startdate):
     from_time=str(int((args.startdate-epoch).total_seconds()))
  if (args.enddate):
     to_time=str(int((args.enddate-epoch).total_seconds()))

  print 'From: %s\nTo: %s\n' %(from_time, to_time)

  scale=1
  unit='seconds since 1.1.1970'
  if (args.attribute == 'temperature'):
     path=temperature_path
     scale = 100
     unit = "Degrees Celsius"
  elif (args.attribute == 'output-power'):
     path=opower_path
     scale = 100
     unit = "Watts"
  elif (args.attribute == 'input-power'):
     path=ipower_path
     scale = 1000
     unit = "Watts"
  else:
     path=motion_path
  print "Epoch Time, Local Time (this machine), Attribute, Value (%s) " % unit
  query_stats(args.host)

The command used to run it:

C:\Python27>python tryme.py -s 2016-03-18 -e 2016-03-19 -u admin -p admin -a motion 192.168.2.222

The results:

Epoch Time, Local Time (this machine), Attribute, Value (seconds since 1.1.1970)
We'll query the host: 192.168.2.222

edited May 17, 2016 at 16:30

answered May 9, 2016 at 14:43

GNewc

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3 Comments

Robin S Over a year ago

This is what I have: def valid_date(s): try: return datetime.strptime(s, "%Y-%m-%d") except ValueError: msg = "Not a valid date (YYYY-MM-DD): '{0}'.".format(s) raise argparse.ArgumentTypeError(msg)

Robin S Over a year ago

The motion_path is defined further up the script - I have only included an excerpt as I thought the problem would be fairly obvious to someone that was familiar with Python. The script executes fine if I take out the -s and -e arguments. If I change the date format it gives me an error to say I've entered the date in the wrong format so that's not the issue either!

GNewc Over a year ago

There is your alternate way to get a unix timestamp (seconds from epoch time).

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