Python Datetime Module Quiz

Naive vs. Aware Datetimes

• Naive datetimes lack timezone or daylight savings time information
• Aware datetimes contain timezone and daylight savings time information
• Naive datetimes easier to use when this level of detail is unnecessary

Working With Days

• datetime.date works with year, month, and day
• Construct a date using datetime.date(year, month, day)
• Access individual attributes using date.year, date.month, date.day
• Get today's local date using datetime.date.today()
• Get weekday using date.weekday() (Monday = 0, Sunday = 6)
• Get ISO weekday using date.isoweekday() (Monday = 1, Sunday = 7)

Time Deltas

• Represent the difference between two dates or times
• Created using datetime.timedelta(days=...)
• Adding or subtracting a timedelta from a date produces a different date
• Adding or subtracting a date from a date produces a timedelta
• Calculate days until an event using birthdate - today.date()

Working with Time

• datetime.time works with hour, minute, second, and microsecond
• Construct a time using datetime.time(hour, minute, second, microsecond)
• Access individual attributes using time.hour, time.minute, time.second
• datetime.time often less used than datetime.datetime for time-related operations

Working with Datetime

• datetime.datetime combines date and time information
• Construct a datetime using datetime.datetime(year, month, day, hour, minute, second, microsecond)
• Access date and time information using datetime.date and datetime.time
• Add or subtract timedelta from a datetime to manipulate time

Alternative Constructors

• datetime.datetime.today() provides current local date and time with TZInfo=None
• datetime.datetime.now() can optionally take a timezone argument when constructing a datetime, otherwise, TZInfo=None
• datetime.datetime.utcnow() provides current UTC time with TZInfo=None
• These constructors are convenient shortcuts for specific time-related information

Time Zones

• Python standard library offers basic timezone handling but pytz library is more practical
• pytz is a third-party library that provides a database of time zones
• Install pytz using pip: pip install pytz
• Always work in UTC when dealing with time zones

Constructing Timezone Aware Datetimes

• Construct a UTC time zone-aware datetime:
  • datetime.datetime(2016, 7, 26, 12, 30, 45, tzinfo=pytz.UTC)
• Get current UTC time zone-aware datetime:
  • datetime.datetime.now(tz=pytz.UTC) or
  • datetime.datetime.utcnow().replace(tzinfo=pytz.UTC)

Converting Between Time Zones

• Convert a UTC datetime to a specific timezone:
  • dt_utc.astimezone(pytz.timezone('US/Mountain'))
• Convert a naive datetime to another timezone is not straightforward
• Using pytz.timezone to manipulate naive datetimes within a specific timezone is not supported.

Exploring Time Zones

• Print all available time zones:
  • for tz in pytz.all_timezones: print(tz)
• This list provides time zones for manipulation using pytz.timezone

Naive DateTimes and Time Zones

• A naive datetime in Python holds no information about the time zone, it's simply a date and time value.

• Python provides a way to make a naive datetime timezone aware by using the localize() method from the tzlocal package.

• To use localize(), you need to know the time zone of the naive datetime, in the example the naive datetime is in Mountain Time.

Converting Between Time Zones

• You can convert a timezone aware datetime to another time zone by using the .astimezone() method.

• This method converts the datetime to the specified time zone and returns a new datetime object with the new time zone information.

Displaying Datetimes

• You can display a datetime in ISO format using the isoformat() method.

• To format a datetime in a specific way, use the strftime() method and pass in a format string that specifies the desired format.

• Format codes are available in the Python documentation and let you convert a datetime to a string.

Converting Strings to Datetimes

• You can convert a string to a datetime using the strptime() method from the datetime package.

• strptime() takes a string and a format string as arguments and returns a datetime object.

• This process is the opposite of strftime(), which converts a datetime to a string.

Arrow Package

• The arrow package is a popular Python library for working with datetimes.

• It's designed to be easier to use than the built-in datetime module.

• For most basic needs, the built-in datetime module is sufficient.