An AWS Cron Parser

## Project description

Main Branch Status

Develop Branch Status

# pyawscron

A python port from a typescript project.

https://github.com/beemhq/aws-cron-parser

# Install

pip install pyawscron


## AWS Cron Expressions

### cron(fields)

Field Values Wildcards

Minutes

0-59

, - * /

Hours

0-23

, - * /

Day-of-month

1-31

, - * ? / L W

Month

1-12 or JAN-DEC

, - * /

Day-of-week

1-7 or SUN-SAT

, - * ? L #

Year

1970-2199

, - * /

### Wildcards

• The , (comma) wildcard includes additional values. In the Month field, JAN,FEB,MAR would include January, February, and March.
• The - (dash) wildcard specifies ranges. In the Day field, 1-15 would include days 1 through 15 of the specified month.
• The * (asterisk) wildcard includes all values in the field. In the Hours field, * would include every hour. You cannot use * in both the Day-of-month and Day-of-week fields. If you use it in one, you must use ? in the other.
• The / (forward slash) wildcard specifies increments. In the Minutes field, you could enter 1/10 to specify every tenth minute, starting from the first minute of the hour (for example, the 11th, 21st, and 31st minute, and so on).
• The ? (question mark) wildcard specifies one or another. In the Day-of-month field you could enter 7 and if you didn't care what day of the week the 7th was, you could enter ? in the Day-of-week field.
• The L wildcard in the Day-of-month or Day-of-week fields specifies the last day of the month or week.
• The W wildcard in the Day-of-month field specifies a weekday. In the Day-of-month field, 3W specifies the weekday closest to the third day of the month.
• The # wildcard in the Day-of-week field specifies a certain instance of the specified day of the week within a month. For example, 3#2 would be the second Tuesday of the month: the 3 refers to Tuesday because it is the third day of each week, and the 2 refers to the second day of that type within the month.

# Iterative Use

next

from pyawscron import AWSCron
import datetime
import calendar

def main():

aws_cron = AWSCron("0 5 4 * ? *")
today = datetime.datetime.utcnow().date()
start_date = datetime.datetime(today.year, today.month, 1, tzinfo=datetime.timezone.utc)
last_day = calendar.monthrange(today.year, today.month)[1]
end_date = datetime.datetime(today.year, today.month, last_day, tzinfo=datetime.timezone.utc)
dt=start_date
while True:
dt = aws_cron.occurrence(dt).next()
if dt > end_date:
break
print(dt)

if __name__ == "__main__":
main()


prev

from pyawscron import AWSCron
import datetime

def main():

aws_cron = AWSCron("0 5 4 * ? *")
today = datetime.datetime.utcnow().date()
start_date = datetime.datetime(today.year, today.month, 1, tzinfo=datetime.timezone.utc)
end_date = datetime.datetime(today.year, today.month-1, 1, tzinfo=datetime.timezone.utc)
dt=start_date
while True:
dt = aws_cron.occurrence(dt).prev()
if dt < end_date:
break
print(dt)

if __name__ == "__main__":
main()


## Helper Methods

### get_all_schedule_bw_dates

Returns a list of UTC datetime objects using a start and end date. The end date has a flag to be inclusive or exclusive.

Note: This method has no limit on how many datetime object can be returned. Use Iterative approach or get_next_n_schedule if memory becomes an issue.

from_dt = datetime.datetime(2021, 8, 7, 8, 30, 57, tzinfo=datetime.timezone.utc)
to_date = datetime.datetime(2021, 8, 7, 11, 30, 57, tzinfo=datetime.timezone.utc)

AWSCron.get_all_schedule_bw_dates(from_dt, to_date, '0/23 * * * ? *')

# Resulting list
[datetime.datetime(2021, 8, 7, 8, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 11, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 11, 23, tzinfo=datetime.timezone.utc)]


### get_next_n_schedule

Returns a list with the n next datetimes that match the aws cron expression from the provided start date.

from_dt = datetime.datetime(2021, 8, 7, 8, 30, 57, tzinfo=datetime.timezone.utc)

AWSCron.get_next_n_schedule(10, from_dt, '0/23 * * * ? *')

# Resulting list
[datetime.datetime(2021, 8, 7, 8, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 11, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 11, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 11, 46, tzinfo=datetime.timezone.utc)]


### get_prev_n_schedule

Returns a list with the n prev datetimes that match the aws cron expression from the provided start date.

from_dt = datetime.datetime(2021, 8, 7, 11, 50, 57, tzinfo=datetime.timezone.utc)

AWSCron.get_prev_n_schedule(10, from_dt, '0/23 * * * ? *')

# Resulting list
[datetime.datetime(2021, 8, 7, 11, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 11, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 11, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 10, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 46, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 23, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 9, 0, tzinfo=datetime.timezone.utc),
datetime.datetime(2021, 8, 7, 8, 46, tzinfo=datetime.timezone.utc)]


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