11.5. Datetime Parse¶

Parsing - analyze (a sentence) into its parts and describe their syntactic roles.

11.5.1. Parsing dates¶

>>> from datetime import datetime

Datetime parsing from string:

>>> x = '1961-04-12 06:07'
>>>
>>> datetime.strptime(x, '%Y-%m-%d %H:%M')
datetime.datetime(1961, 4, 12, 6, 7)

11.5.2. Leading Zero¶

Mind that while parsing dates without leading zero, you do not use %#H or %-H as it was for formatting. One should simply use %H to capture hour:

>>> x = '1961-04-12 6:07'
>>>
>>> datetime.strptime(x, '%Y-%m-%d %H:%M')
datetime.datetime(1961, 4, 12, 6, 7)

11.5.3. String Fitting¶

If there are any other characters in the string, such as commas, brackets spaces, colons, dashes etc, they should be reflected in the format string.

>>> x = 'Apr 12th, 1961 6:07 am'
>>>
>>> datetime.strptime(x, '%b %dth, %Y %I:%M %p')
datetime.datetime(1961, 4, 12, 6, 7)

>>> x = '12 April 1961 at 6:07 am'
>>>
>>> datetime.strptime(x, '%d %B %Y at %I:%M %p')
datetime.datetime(1961, 4, 12, 6, 7)

Omitting any of those values will result with an error:

>>> x = '12 April 1961 at 6:07 am'
>>>
>>> datetime.strptime(x, '%d %B %Y %I:%M %p')
Traceback (most recent call last):
ValueError: time data '12 April 1961 at 6:07 am' does not match format '%d %B %Y %I:%M %p'

11.5.4. Time Zone¶

More information in Datetime Timezone

>>> x = '12 April 1961 6:07 UTC'
>>>
>>> datetime.strptime(x, '%d %B %Y %H:%M %Z')
datetime.datetime(1961, 4, 12, 6, 7)

>>> x = '1961-04-12 6:07 local'
>>>
>>> datetime.strptime(x, '%Y-%m-%d %H:%M')
Traceback (most recent call last):
ValueError: unconverted data remains:  local

>>> x = '1961-04-12 6:07 local'
>>>
>>> datetime.strptime(x, '%Y-%m-%d %H:%M %Z')
Traceback (most recent call last):
ValueError: time data '1961-04-12 6:07 local' does not match format '%Y-%m-%d %H:%M %Z'

>>> x = '1961-04-12 6:07 local'
>>>
>>> datetime.strptime(x, '%Y-%m-%d %H:%M local')
datetime.datetime(1961, 4, 12, 6, 7)

11.5.5. Parsing Parameters¶

Table 11.3. Date and time parsing parameters¶
Directive	Example	Meaning
`%a`	Sun, Mon, ..., Sat	Weekday as locale's abbreviated name
`%A`	Sunday, Monday, ..., Saturday (en_US)	Weekday as locale's full name
`%w`	0, 1, ..., 6	Weekday as a decimal number, where 0 is Sunday and 6 is Saturday
`%d`	01, 02, ..., 31	Day of the month as a zero-padded decimal number
`%b`	Jan, Feb, ..., Dec (en_US)	Month as locale's abbreviated name
`%B`	January, February, ..., December (en_US)	Month as locale's full name
`%m`	01, 02, ..., 12	Month as a zero-padded decimal number
`%y`	00, 01, ..., 99	Year without century as a zero-padded decimal number
`%Y`	0001, 0002, ..., 2013, 2014, ..., 9998, 9999	Year with century as a decimal number
`%H`	00, 01, ..., 23	Hour (24-hour clock) as a zero-padded decimal number
`%I`	01, 02, ..., 12	Hour (12-hour clock) as a zero-padded decimal number
`%p`	AM, PM (en_US)	Locale's equivalent of either AM or PM
`%M`	00, 01, ..., 59	Minute as a zero-padded decimal number
`%S`	00, 01, ..., 59	Second as a zero-padded decimal number
`%f`	000000, 000001, ..., 999999	Microsecond as a decimal number, zero-padded on the left
`%z`	(empty), +0000, -0400, +1030	UTC offset in the form +HHMM or -HHMM (empty string if the object is naive)
`%Z`	(empty), UTC, EST, CST	Time zone name (empty string if the object is naive)
`%j`	001, 002, ..., 366	Day of the year as a zero-padded decimal number
`%U`	00, 01, ..., 53	Week number of the year (Sunday as the first day of the week) as a zero padded decimal number. All days in a new year preceding the first Sunday are considered to be in week 0
`%W`	00, 01, ..., 53	Week number of the year (Monday as the first day of the week) as a decimal number. All days in a new year preceding the first Monday are considered to be in week 0
`%c`	Tue Aug 16 21:30:00 1988 (en_US)	Locale's appropriate date and time representation
`%x`	08/16/1988 (en_US); 16.08.1988 (de_DE)	Locale's appropriate date representation
`%X`	21:30:00	Locale's appropriate time representation
`%%`	%	A literal `%` character
`%G`	0001, 0002, ..., 2013, 2014, ..., 9998, 9999	ISO 8601 year with century representing the year that contains the greater part of the ISO week (`%V`)
`%u`	1, 2, ..., 7	ISO 8601 weekday as a decimal number where 1 is Monday
`%V`	01, 02, ..., 53	ISO 8601 week as a decimal number with Monday as the first day of the week. Week 01 is the week containing Jan 4

11.5.6. Assignments¶

Code 11.31. Solution¶

"""
* Assignment: Datetime Parse US
* Complexity: easy
* Lines of code: 1 lines
* Time: 3 min

English:
    1. Define `result: datetime` with parsed date `DATA`
    2. Run doctests - all must succeed

Polish:
    1. Zdefiniuj `result: datetime` ze sparsowaną datą `DATA`
    2. Uruchom doctesty - wszystkie muszą się powieść

Hints:
    * 12-hour clock

Tests:
    >>> import sys; sys.tracebacklimit = 0

    >>> assert result is not Ellipsis, \
    'Assign result to variable: `result`'
    >>> assert type(result) is datetime, \
    'Variable `result` has invalid type, must be a datetime'

    >>> result
    datetime.datetime(1969, 7, 21, 2, 56, 15)
"""

from datetime import datetime


DATA = 'July 21, 1969 2:56:15 AM'

# DATA from US long format
# type: datetime
result = ...

Code 11.32. Solution¶

"""
* Assignment: Datetime Parse Ordinals
* Complexity: easy
* Lines of code: 1 lines
* Time: 3 min

English:
    1. Define `result: datetime` with parsed date `DATA`
    2. Run doctests - all must succeed

Polish:
    1. Zdefiniuj `result: datetime` ze sparsowaną datą `DATA`
    2. Uruchom doctesty - wszystkie muszą się powieść

Hints:
    * 12-hour clock
    * `%dst`

Tests:
    >>> import sys; sys.tracebacklimit = 0

    >>> assert result is not Ellipsis, \
    'Assign result to variable: `result`'
    >>> assert type(result) is datetime, \
    'Variable `result` has invalid type, must be a datetime'

    >>> result
    datetime.datetime(1969, 7, 21, 2, 56, 15)
"""

from datetime import datetime


DATA = 'July 21st, 1969 2:56:15 AM'

# DATA from long US format with ordinals
# type: datetime
result = ...

Code 11.33. Solution¶

"""
* Assignment: Datetime Parse List
* Complexity: medium
* Lines of code: 8 lines
* Time: 3 min

English:
    1. Define `result: list[date]` with parsed `DATA` dates
    2. Run doctests - all must succeed

Polish:
    1. Zdefiniuj `result: list[date]` ze sparsowanymi datami `DATA`
    2. Uruchom doctesty - wszystkie muszą się powieść

Hints:
    * `for ... in`
    * `try ... except`
    * ``dt.strptime()``
    * ``dt.date()``
    * ``list.append()``
    * 24-hour clock

Tests:
    >>> import sys; sys.tracebacklimit = 0
    >>> from pprint import pprint
    >>> result = list(result)

    >>> assert result is not Ellipsis, \
    'Assign result to variable: `result`'
    >>> assert type(result) is list, \
    'Variable `result` has invalid type, must be a list'
    >>> assert all(type(element) is date for element in result), \
    'All elements in `result` must be a date'

    >>> pprint(result, width=30)
    [datetime.date(1957, 10, 4),
     datetime.date(1961, 4, 12)]
"""

from datetime import date, datetime


DATA = [
    'October 4, 1957',  # Sputnik launch (first satellite in space)
    'Apr 12, 1961',  # Gagarin launch (first human in space)
]

# parsed DATA
# type: list[date]
result = ...

Code 11.34. Solution¶

"""
* Assignment: Datetime Parse Many
* Complexity: medium
* Lines of code: 12 lines
* Time: 5 min

English:
    1. Define `result: list[datetime]` with parsed `DATA` dates
    2. Run doctests - all must succeed

Polish:
    1. Zdefiniuj `result: list[datetime]` ze sparsowanymi datami `DATA`
    2. Uruchom doctesty - wszystkie muszą się powieść

Hints:
    * `for ... in`
    * nested `try ... except`
    * FORMATS = []
    * for fmt in FORMATS
    * helper function
    * 24-hour clock

Tests:
    >>> import sys; sys.tracebacklimit = 0

    >>> assert result is not Ellipsis, \
    'Assign result to variable: `result`'
    >>> result = list(result)
    >>> assert type(result) is list, \
    'Variable `result` has invalid type, must be a list'
    >>> assert all(type(element) is datetime for element in result), \
    'All elements in `result` must be a datetime'

    >>> result  # doctest: +NORMALIZE_WHITESPACE
    [datetime.datetime(1957, 10, 4, 19, 28, 34),
     datetime.datetime(1961, 4, 12, 6, 7),
     datetime.datetime(1969, 7, 21, 2, 56, 15)]
"""

from datetime import datetime


DATA = [
    'Oct 4, 1957 19:28:34',  # Sputnik launch (first satellite in space)
    'April 12, 1961 6:07',  # Gagarin launch (first human in space)
    'July 21, 1969 2:56:15',  # Armstrong first step on the Moon
]

FORMATS = [
    '%b %d, %Y %H:%M:%S',
    '%B %d, %Y %H:%M',
    '%B %d, %Y %H:%M:%S',
]


# DATA elements in datetime format
# type: list[datetime]
result = ...