Python passing variable dates to function

Question

Hello: making progress but still struggling. I have the following json:

json =
{
  "emeter": {
    "get_daystat": {
      "day_list": [
        { "year": 2016, "month": 10, "day": 1, "energy": 0.651000 },
        { "year": 2016, "month": 10, "day": 2, "energy": 0.349000 },
        { "year": 2016, "month": 10, "day": 3, "energy": 0.481000 }
      ],
      "err_code": 0
    }
  }
}

I am using a linear search to find the energy value from a specific day with this function:

parsed_json = json.loads(json)

def get_energy_value_by_date(obj, year, month, day):   
    for value in obj['emeter']['get_daystat']['day_list']:
        if value['year'] == year and value['month'] == month and value['day'] == day:
            return value['energy']


energy = get_energy_value_by_date(parsed_json, 2016, 10, 2)

So far so good. What I need to do next is find the energy value for various days. For example today (assume json is valid):

import datetime
day_now = datetime.datetime.now().strftime("%d")
month_now = datetime.datetime.now().strftime("%m")
year_now = datetime.datetime.now().strftime("%Y")

parsed_json = json.loads(json)

def get_energy_value_by_date(obj, year, month, day):   
    for value in obj['emeter']['get_daystat']['day_list']:
        if value['year'] == year and value['month'] == month and value['day'] == day:
            return value['energy']


energy_today = get_energy_value_by_date(parsed_json, year_now, month_now, day_now)
print energy_today

When I run this script it returns

None

I must be missing something basic here. What I need is the ability to pull the energy value for any day of any month of any year for further processing.

Thanks!

Baobab

print day_now, month_now etc. Debug from there.

Dan
– Dan

2016-10-04 14:52:59 +00:00
Commented Oct 4, 2016 at 14:52 — Dan
– Dan, Commented Oct 4, 2016 at 14:52
The problem is you need to cast your variables to ints.

Dan
– Dan

2016-10-04 14:55:34 +00:00
Commented Oct 4, 2016 at 14:55 — Dan
– Dan, Commented Oct 4, 2016 at 14:55

brianpck · Accepted Answer · 2016-10-04 15:25:24Z

2

There is a simple issue with your script: strftime, according to the docs, will

return a string representing the date, controlled by an explicit format string.

The keyword here being "string." See the following:

>>> import datetime
>>> day_now = datetime.datetime.now().strftime("%d")
>>> day_now
'04'

This does not equal the integer value of the day in your JSON file:

>>> '04' == 4
False

Therefore, the equality check will always fail and None will be returned. One way is to use int to convert this value to an integer. A better way is to use the attributes of a datetime object to get the integer values:

>>> datetime.datetime.now().year
2016
>>> datetime.datetime.now().month
10
>>> datetime.datetime.now().day
4

I would also advise passing just a date object to the function and unpacking it there: it prevents redundancy and cleans up the function signature. You should also use date.today() instead of datetime.now() (since time is irrelevant) and then make the comparison in one operation. The full function could be something like this:

def get_energy_value_by_date(obj, current_day):   
    for value in obj['emeter']['get_daystat']['day_list']:
        if current_day == datetime.date(value['year'], value['month'], value['day']):
            return value['energy']

current_day = datetime.date.today()
energy_today = get_energy_value_by_date(parsed_json, current_day)
print (energy_today)

edited Oct 4, 2016 at 15:25

answered Oct 4, 2016 at 14:54

brianpck

8,3241 gold badge25 silver badges34 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

brianpck Over a year ago

@Baobab I edited my last function to include some simper logic--take a look at that as well!

Collectives™ on Stack Overflow

Python passing variable dates to function

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related