How do I validate a date string format in python

Question

I have a python method which accepts a date input as a string   How do I add a validation to make sure the date string being passed to the method is in the ffg  format    YYYY-MM-DD    if it s not  method should raise some sort of error

User · Answer

from datetime import datetime  datetime strptime date string    Y- m- d       this raises a ValueError if it receives an incompatible format     if you re dealing with dates and times a lot  in the sense of datetime objects  as opposed to unix timestamp floats   it s a good idea to look into the pytz module  and for storage db  store everything in UTC

User · Answer

From mere curiosity  I timed the two rivalling answers posted above  And I had the following results  dateutil parser  valid str   4 6732222699938575 dateutil parser  invalid str   1 7270505399937974 datetime strptime  valid   0 7822393209935399 datetime strptime  invalid   0 4394566189876059  And here s the code I used  Python 3 6   from dateutil import parser as date parser from datetime import datetime from timeit import timeit   def is date parsing date str       try          return bool date parser parse date str       except ValueError          return False   def is date matching date str       try          return bool datetime strptime date str    Y- m- d        except ValueError          return False    if   name         main         print  quot dateutil parser  valid date   quot   end          print timeit  quot is date parsing  2021-01-26   quot                    setup  quot from   main   import is date parsing quot                    number 100000        print  quot dateutil parser  invalid date   quot   end          print timeit  quot is date parsing  meh   quot                    setup  quot from   main   import is date parsing quot                    number 100000        print  quot datetime strptime  valid date   quot   end          print timeit  quot is date matching  2021-01-26   quot                    setup  quot from   main   import is date matching quot                    number 100000        print  quot datetime strptime  invalid date   quot   end          print timeit  quot is date matching  meh   quot                    setup  quot from   main   import is date matching quot                    number 100000

User · Answer

gt  gt  gt  import datetime  gt  gt  gt  def validate date text       try          datetime datetime strptime date text    Y- m- d       except ValueError          raise ValueError  Incorrect data format  should be YYYY-MM-DD      gt  gt  gt  validate  2003-12-23    gt  gt  gt  validate  2003-12-32    Traceback  most recent call last     File   lt pyshell 20 gt    line 1  in  lt module gt      validate  2003-12-32     File   lt pyshell 18 gt    line 5  in validate     raise ValueError  Incorrect data format  should be YYYY-MM-DD   ValueError  Incorrect data format  should be YYYY-MM-DD

User · Answer

The Python dateutil library is designed for this  and more   It will automatically convert this to a datetime object for you and raise a ValueError if it can t   As an example    gt  gt  gt  from dateutil parser import parse  gt  gt  gt  parse  2003-09-25   datetime datetime 2003  9  25  0  0    This raises a ValueError if the date is not formatted correctly    gt  gt  gt  parse  2003-09-251   Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt    File   Users jacinda envs dod-backend-dev lib python2 7 site-packages dateutil parser py   line 720  in parse     return DEFAULTPARSER parse timestr    kwargs    File   Users jacinda envs dod-backend-dev lib python2 7 site-packages dateutil parser py   line 317  in parse     ret   default replace   repl  ValueError  day is out of range for month   dateutil is also extremely useful if you start needing to parse other formats in the future  as it can handle most known formats intelligently and allows you to modify your specification  dateutil parsing examples     It also handles timezones if you need that   Update based on comments  parse also accepts the keyword argument dayfirst which controls whether the day or month is expected to come first if a date is ambiguous  This defaults to False  E g    gt  gt  gt  parse  11 12 2001    gt  gt  gt  datetime datetime 2001  11  12  0  0    Nov 12  gt  gt  gt  parse  11 12 2001   dayfirst True   gt  gt  gt  datetime datetime 2001  12  11  0  0    Dec 11

User · Answer

I think the full validate function should look like this   from datetime import datetime  def validate date text       try          if date text    datetime strptime date text    Y- m- d   strftime   Y- m- d                raise ValueError         return True     except ValueError          return False   Executing just   datetime strptime date text    Y- m- d      is not enough because strptime method doesn t check that month and day of the month are zero-padded decimal numbers  For example  datetime strptime  2016-5-3     Y- m- d     will be executed without errors

[python] How do I validate a date string format in python?

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