Formatting dates within a Python dict

Question

 if not all(key in payload for key in payloads[template]):
        raise InvalidPayloadException

    if 'order_date' in payload:
        payload['order_date'] = self._get_formatted_date(payload['order_date'])

    if 'payment_date' in payload:
        payload['payment_date'] = self._get_formatted_date(payload['payment_date'])

    if 'shipped_date' in payload:
        payload['shipped_date'] = self._get_formatted_date(payload['shipped_date'])

I have some code that triggers a PDF generation. It accepts a python dict that contains the payload for the PDF.

There are a good few number of dates that need to be displayed in the PDF but not all documents contain all PDFs. I need to format the dates before sending it to the PDF. At the moment my code is a lot of different IF statements to catch all the possible dates and format them in the dict.

Is there a more pythonic way to do it?

score 4 · Accepted Answer · answered Dec 11 '17 at 10:56

4

Use a loop.

for date_key in ('order_date', 'payment_date', 'shipped_date'):
    if date_key in payload:
        payload[date_key] = self._get_formatted_date(payload[date_key])

answered Dec 11 '17 at 10:56

Daniel Roseman

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DeepSpace · Answer 2 · 2017-12-11T11:03:46.240

1

You don't need any of the if statements.

A common methodology in Python is EAFP (Easier to Ask for Forgiveness than Permission) rather than LBYL (Look Before You Leap). Hence you should prepare a tuple or list of keys you expect to be in the payload dict, and use try-except in case one of the keys is missing.

for key in ('order_date', 'payment_date', 'shipped_date'):
    try:
        payload[key] = self._get_formatted_date(payload[key])
    except KeyError:
        print('{} not in payload dict'.format(key))

edited Dec 11 '17 at 11:03

answered Dec 11 '17 at 10:56

DeepSpace

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1

Exception handling is not a conditional so checking if something exists is cleaner. See [here](https://stackoverflow.com/questions/4512557/python-if-key-in-dict-vs-try-except) for more explanation – Ivonet Dec 11 '17 at 11:03
Yet is less Pythonic, and OP ask for a Pythonic approach. It also depends what is expected to happen more, an existing key or a missing key. – DeepSpace Dec 11 '17 at 11:05
1

EAFP is fine when you know exceptions will be, well, exceptional (or when you can have a race condition, which is not the point here). And __NO__, blindly using potentially expensive try/excepts just because someone once said it was "pythonic" when there's a way cheaper solution and no possible race condition is __definitly NOT__ pythonic. – bruno desthuilliers Dec 11 '17 at 11:06
EAFP is fine, don't know why people have such a big issue with it. This answer is great since it shows another perspective to the problem. – RoadRunner Dec 11 '17 at 11:36

score 0 · Answer 3 · answered Dec 11 '17 at 11:02

0

You could created a tuple of date keys and use a for loop.

date_keys = ("order_date", "payment_date", "shipped_date")

for date_key in date_keys:
    if date_key in payload:
        payload[date_key] = self._get_formatted_date(payload[date_key])

answered Dec 11 '17 at 11:02

ramchauhan

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score -1 · Answer 4 · answered Dec 11 '17 at 10:58

-1

You could create a list of all possible dates to format and iterate over them

dates = [
    "order_date",
    "payment_date",
    "shipped_date"
]

for d in dates:
    if d in payload:
       payload[d] = self._get_formatted_date(payload[d])

answered Dec 11 '17 at 10:58

Ivonet

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Formatting dates within a Python dict

4 Answers4