61 lines
1.8 KiB
Plaintext
61 lines
1.8 KiB
Plaintext
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This rule raises an issue when the functions `datetime.datetime.utcnow` or `datetime.datetime.utcfromtimestamp` are used.
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== Why is this an issue?
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Python's `datetime` API provide several different ways to create `datetime` objects. One possibility is the to use
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`datetime.datetime.utcnow` or `datetime.datetime.utcfromtimestamp` functions. The issue with these two functions is they are not time zone aware, even if their name would suggest otherwise.
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Using these functions could cause issue as they may not behave as expected, for example:
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[source,python]
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----
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from datetime import datetime
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timestamp = 1571595618.0
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date = datetime.utcfromtimestamp(timestamp)
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date_timestamp = date.timestamp()
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assert timestamp == date_timestamp
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----
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This assertion will fail if the system locale is not set to UTC.
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For this reason these 2 functions are deprecated in Python 3.12.
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== How to fix it
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To fix this issue, prefer the usage of a timezone-aware datetime.
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=== Code examples
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==== Noncompliant code example
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[source,python,diff-id=1,diff-type=noncompliant]
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----
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from datetime import datetime
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datetime.utcnow() # Noncompliant
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timestamp = 1571595618.0
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datetime.utcfromtimestamp(timestamp) # Noncompliant
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----
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==== Compliant solution
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[source,python,diff-id=1,diff-type=compliant]
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----
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from datetime import datetime, timezone
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datetime.now(timezone.utc) # Compliant
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timestamp = 1571595618.0
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datetime.fromtimestamp(timestamp, timezone.utc) # Compliant
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----
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== Resources
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=== Documentation
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* Python documentation - https://docs.python.org/3/library/datetime.html#datetime.datetime.utcnow[utcnow reference]
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* Python documentation - https://docs.python.org/3/library/datetime.html#datetime.datetime.utcfromtimestamp[utcfromtimestamp reference]
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=== Articles & blog posts
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* Paul Ganssle blog - https://blog.ganssle.io/articles/2019/11/utcnow.html[Stop using utcnow and utcfromtimestamp]
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