从字符串转换为 ISO 时间格式不起作用

Question

Been trying to set a time range of 15 min between now and 15 minutes before. So far no problem. Here is the code:

from datetime import datetime 

now = datetime.now()
past15min = (now - timedelta(minutes=15)).isoformat()[:-3] + 'Z'

print(type(now),now)
print(type(past15min),past15min)

Output:

<class 'datetime.datetime'> 2022-12-21 17:51:18.233462
<class 'str'> 2022-12-21T17:36:18.233Z

Now, the issue is that I need it to be strictly in ISO format that ends with 3 digits + the letter Z at the end. I'm using this as part of another language Elastic DSL. There, I'm using the variable now in the beginning timerange, and the variable past15min in the end timerange. What happens is that now is in datetime format and end in 6 digits. If I try to type cast it into a string, then the calculation in the past15min variable won't work since you can't subtract strings.

now = str(datetime.now())
past15min = (now - timedelta(minutes=15)).isoformat()[:-3] + 'Z'

print(type(now),now)
print(type(past15min),past15min)

Output:

    past15min = (now - timedelta(minutes=15)).isoformat()[:-3] + 'Z'
TypeError: unsupported operand type(s) for -: 'str' and 'datetime.timedelta'

I also tried to first edit the time into its correct format, which turns it into a string automatically, and then convert it into iso format again to I can do the calculation, but I get an error still.

now = datetime.now().isoformat()[:-3] + 'Z'
now_to_datetime = datetime(now)
past15min = (now_to_datetime - timedelta(minutes=15)).isoformat()[:-3] + 'Z'

print(type(now),now)
print(now_to_datetime)
print(type(past15min),past15min)

Output:

    now_to_datetime = datetime(now)
TypeError: 'str' object cannot be interpreted as an integer

Any help is appreciated.

Answer 1

Only format the datetimes into a string before printing.

from datetime import datetime, timedelta
now = datetime.now()
past15min = (now - timedelta(minutes=15))

print(type(now),now.isoformat(timespec='milliseconds') + 'Z')
print(type(past15min),past15min.isoformat(timespec='milliseconds') + 'Z')

Answer 2

Why don't you do the string formatting after you perform the calculations?

now = datetime.utcnow()
past15min = (now - timedelta(minutes=15))

formatted_now = now.isoformat()[:-3] + 'Z' # '2022-12-21T09:22:34.213Z'
formatted_past15min = past15min.isoformat()[:-3] + 'Z' # '2022-12-21T09:07:34.213Z'

You can now send the formatted data to whatever external system you want.