Python: define a string variable pattern

Question

I'm new to python.

I have a program that reads from str(sys.argv[1]):

myprogram.py "some date" # I'd like this in YYYYMMDD format. I.e:
myprogram.py 20160806


if __name__ == '__main__':
    if str(sys.argv[1]):
        CTRL = str(sys.argv[1])
        print "some stuff"
        sys.exit()

I need "some date" in YYYYMMDD format. How could it be possible? I've googled variable mask, variable pattern and nothing came out.

Thanks for your help and patience.

UPDATE:

Fortunately all answers helped me!

As the CTRL variable gaves me 2016-08-17 00:00:00 format, I had to convert it to 20160817. Here is the code that worked for me:

if str(sys.argv[1]):
    CTRL_args = str(sys.argv[1])

    try:
        CTRL = str(datetime.datetime.strptime(CTRL_args, "%Y%m%d")).strip().split(" ")[0].replace("-","").replace(" ","").replace(":","")
        # do some stuff
    except ValueError:
        print('Wrong format!')
        sys.exit()

'I need "some date" in YYYYMMDD format'. What is "some date"? It doesn't appear anywhere in your code. — Kevin
– Kevin, Commented Aug 18, 2016 at 14:18
It's a little clearer, but "20160806" is already in YYYYMMDD format. What kind of output are you trying to produce? Should your program say "that input is in YYYYMMDD format, great job"? If the user enters "myprogram.py spamAndEggs", should it say "that's not a YYYYMMDD date, try again"? Or what? I still don't know what you're actually trying to do. — Kevin
– Kevin, Commented Aug 18, 2016 at 14:32

g1zmo · Accepted Answer · 2016-08-18 14:44:58Z

2

you need function datetime.strptime with mask %Y%m%d

import sys
from datetime import datetime

if __name__ == '__main__':
    if str(sys.argv[1]):
        CTRL = str(sys.argv[1])
        try:
            print datetime.strptime(CTRL, "%Y%m%d")
        except ValueError:
            print 'Wrong format'
        sys.exit()

Output:

$ python example.py 20160817
2016-08-17 00:00:00

edited Aug 18, 2016 at 14:44

answered Aug 18, 2016 at 14:24

g1zmo

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2 Comments

Fabricio Carboni Over a year ago

How could I put this on the ifstatement to ensure it's not entered in different format?

g1zmo Over a year ago

I added validation to original answer

tpvasconcelos · Accepted Answer · 2016-09-08 00:24:44Z

0

If I understand what you said right, you want to pass an argument in a YYYYMMDD format.

There is nothing stopping you from doing this with your script.

You can run: python yourscript.py YYYYMMDD and a string "YYYYMMDD" will be stored in your CTRL variable.

UPDATE:

The following routine does the checks you are asking for:

Let me know if you need me to explain any of it!

import sys
from datetime import datetime

if __name__ == '__main__':
    try:
        CTRL = str(sys.argv[1])
    except IndexError:
        print "You have not specified a date!"
        sys.exit()

    try:
        parced_CTRL = datetime.strptime(CTRL, "%Y%m%d")
    except ValueError:
        print "Please input date in the YYYYMMDD format!"
        sys.exit()

    print "Date is in the correct format!"
    print "Data = {}".format(parced_CTRL)

UPDATE:

If you want to parse dates in the YYYY-MM-DD format you need to do this instead:

parced_CTRL = datetime.strptime(CTRL, "%Y-%m-%d")

I think it is self explanatory... ;)

edited Sep 8, 2016 at 0:24

answered Aug 18, 2016 at 14:23

tpvasconcelos

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5 Comments

Fabricio Carboni Over a year ago

that's exactly it does. But the parameter should be in YYYYMMDD format, nothing different that that

tpvasconcelos Over a year ago

so you want to check if the format is correct? and if it is not, you want and "error message" output?

Fabricio Carboni Over a year ago

If the format is in YYYYMMDD format do other stuff otherwise print the error message. I haven't wrote that in my question to keep it simple.

tpvasconcelos Over a year ago

Is this what you were looking for?

Fabricio Carboni Over a year ago

It worked! But I had to convert the string 2016-08-17 00:00:00 to 20160817 using

CTRL = str(datetime.datetime.strptime(parced_CTRL, "%Y%m%d")).strip().split(" ")[0].replace("-","").replace(" ","").replace(":","")

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