Python homework assignment. Need help with these functions, thanks.

import os ''' IMPORTANT NOTE: Do NOT change any of the function names or their signatures (the parameters they take). Your functions must behave exactly as described. Please check correctness by running DocTests included in function headers. You may not use any print or input statements in your code. Manage a calendar database. A calendar is a dictionary keyed by date ("YYYY-MM-DD") with value being a list of strings, the events on the specified date. Example: calendar["2017-10-12"] # is a list of events on "2017-10-12" calendar["2017-10-12"]==["Eye doctor", "lunch with sid", "dinner with jane"] ''' # ----------------------------------------------------------------------------- # Please implement the following calendar commands # -----------------------------------------------------------------------------  def command_help(): '''  () -> str  This function is already implemented. Please do not change it.  Returns a help message for the system. That is...  '''   help = """ Help for Calendar. The calendar commands are add DATE DETAILS add the event DETAILS at the specified DATE show show all events in the claendar delete DATE NUMBER delete the specified event (by NUMBER) from the calendar quit quit this program help display this help message Examples: user data follows command: command: add 2017-10-12 dinner with jane added command: show 2017-10-12: 0: Eye doctor 1: lunch with sid 2: dinner with jane 2017-10-29: 0: Change oil in blue car 1: Fix tree near front walkway 2: Get salad stuff, leuttice, red peppers, green peppers 2017-11-06: 0: Sid's birthday command: delete 2017-10-29 2 deleted A DATE has the form YYYY-MM-DD, for example 2017-12-21 2016-01-02 Event DETAILS consist of alphabetic characters, no tabs or newlines allowed. """ return help def command_add(date, event_details, calendar): '''  (str, str, dict) -> str  Add event_details to the list at calendar[date]  Create date if it was not there   date: A string date formatted as "YYYY-MM-DD"  event_details: A string describing the event  calendar: The calendar database  return: empty string   >>> calendar = {}  >>> command_add("2017-02-28", "Python class", calendar)  ''  >>> calendar == {'2017-02-28': ['Python class']}  True  >>> command_add("2017-03-11", "CSCA08 test 2", calendar)  ''  >>> calendar == {'2017-03-11': ['CSCA08 test 2'], '2017-02-28':\  ['Python class']}  True  >>> command_add("2017-03-11", "go out with friends after test", calendar)  ''  >>> calendar == {'2017-03-11': ['CSCA08 test 2', \  'go out with friends after test'], '2017-02-28': ['Python class']}  True  >>>   '''   # YOUR CODE GOES HERE   pass def command_show(calendar): r'''  (dict) -> str  Returns the list of events for calendar sorted in increasing date order  as a string, see examples below for a sample formatting  calendar: the database of events   Example:  >>> calendar = {}  >>> command_add("2017-02-12", "Eye doctor", calendar)  ''  >>> command_add("2017-02-12", "lunch with sid", calendar)  ''  >>> command_add("2017-03-29", "Change oil in blue car", calendar)  ''  >>> command_add("2017-02-12", "dinner with Jane", calendar)  ''  >>> command_add("2017-03-29", "Fix tree near front walkway", calendar)  ''  >>> command_add("2017-03-29", "Get salad stuff", calendar)  ''  >>> command_add("2017-05-06", "Sid's birthday", calendar)  ''  >>> command_show(calendar)  " 2017-02-12: 0: Eye doctor 1: lunch with sid 2: dinner with Jane 2017-03-29: 0: Change oil in blue car 1: Fix tree near front walkway 2: Get salad stuff 2017-05-06: 0: Sid's birthday"  '''  # Hint: Don't use \t (the tab character) to indent, or DocTest will fail  # in the above testcase.  # Put 4 spaces before the date, 8 spaces before each item.   pass def command_delete(date, entry_number, calendar): '''  (str, int, dict) -> str  Delete the entry at calendar[date][entry_number]  If calendar[date] is empty, remove this date from the calendar.  If the entry does not exist, do nothing  date: A string date formatted as "YYYY-MM-DD"  entry_number: An integer indicating the entry in calendar[date] to delete  calendar: The calendar database  return: a string indicating any errors, "" for no errors   Example:   >>> calendar = {}  >>> command_add("2017-02-28", "Python class", calendar)  ''  >>> calendar == {'2017-02-28': ['Python class']}  True  >>> command_add("2017-03-11", "CSCA08 test 2", calendar)  ''  >>> calendar == {'2017-03-11': ['CSCA08 test 2'], '2017-02-28':\  ['Python class']}  True  >>> command_add("2017-03-11", "go out with friends after test", calendar)  ''  >>> calendar == {'2017-03-11': ['CSCA08 test 2', \  'go out with friends after test'], '2017-02-28': ['Python class']}  True  >>> command_delete("2015-01-01", 1, calendar)  '2015-01-01 is not a date in the calendar'  >>> command_delete("2017-03-11", 3, calendar)  'There is no entry 3 on date 2017-03-11 in the calendar'  >>> command_delete("2017-02-28", 0, calendar)  ''  >>> calendar == {'2017-03-11': ['CSCA08 test 2', \  'go out with friends after test']}  True  >>> command_delete("2017-03-11", 0, calendar)  ''  >>> calendar == {'2017-03-11': ['go out with friends after test']}  True  >>> command_delete("2017-03-11", 0, calendar)  ''  >>> calendar == {}  True   '''   # YOUR CODE GOES HERE  pass # ----------------------------------------------------------------------------- # Functions dealing with calendar persistence # -----------------------------------------------------------------------------  ''' The calendar is read and written to disk. ... date_i is "YYYY-MM-DD"' description can not have tab or new line characters in them. ''' def save_calendar(calendar): '''  (dict) -> bool  Save calendar to 'calendar.txt', overwriting it if it already exists.   The format of calendar.txt is the following:   date_1:description_1\tdescription_2\t...\tdescription_n  date_2:description_1\tdescription_2\t...\tdescription_n  date_3:description_1\tdescription_2\t...\tdescription_n  date_4:description_1\tdescription_2\t...\tdescription_n  date_5:description_1\tdescription_2\t...\tdescription_n   Example: The following calendar...   2017-02-28:  0: Python class  2017-03-11:  0: CSCA08 test 2  1: go out with friends after test   appears in calendar.txt as ...   2017-02-28:Python class  2017-03-11:CSCA08 test 2 go out with friends after test   calendar: dictionary containing a calendar  return: True if the calendar was saved.  Normally we should return False otherwise, however we have not  learned yet how to handle errors. Therefore there will be no testing  for cases when the save_calendar operation can fail. Also there is no  need to provide error handling code. You may if you like, however  no extra credit will be given, and additionally, you may have to  explain to the grader/instructor in full how did you do the handling.  '''  # YOUR CODE GOES HERE  pass def load_calendar(): '''  () -> dict  Load calendar from 'calendar.txt'. If calendar.txt does not exist,  create and return an empty calendar. For the format of calendar.txt  see save_calendar() above. Please observe there are cases when  the load_calendar operation can fail. There is no  need to provide error handling code. You may if you like, however  no extra credit will be given, and additionally, you may have to  explain to the grader/instructor in full how did you do the handling.  In case you decide to do error handling, you must return an empty  calendar in case of various errors.   return: calendar.   '''   # YOUR CODE GOES HERE  pass # ----------------------------------------------------------------------------- # Functions dealing with parsing commands # -----------------------------------------------------------------------------  def is_command(command): '''  (str) -> bool  Return whether command is indeed a command, that is, one of  "add", "delete", "quit", "help", "show"  You are not allowed to use regular expressions in your implementation.  command: string  return: True if command is one of ["add", "delete", "quit", "help", "show"]  false otherwise  Example:  >>> is_command("add")  True  >>> is_command(" add ")  False  >>> is_command("List")  False   '''   # YOUR CODE GOES HERE  pass def is_calendar_date(date): '''  (str) -> bool  Return whether date looks like a calendar date  date: a string  return: True, if date has the form "YYYY-MM-DD" and False otherwise  You are not allowed to use regular expressions in your implementation.  Also you are not allowed to use isdigit() or similar functions.   Example:   >>> is_calendar_date("15-10-10") # invalid year  False  >>> is_calendar_date("2015-10-15")  True  >>> is_calendar_date("2015-5-10") # invalid month  False  >>> is_calendar_date("2015-15-10") # invalid month  False  >>> is_calendar_date("2015-05-10")  True  >>> is_calendar_date("2015-10-55") # invalid day  False  >>> is_calendar_date("2015-55") # invalid format  False  >>> is_calendar_date("jane-is-gg") # YYYY, MM, DD should all be digits  False   Note: This does not validate days of the month, or leap year dates.   >>> is_calendar_date("2015-04-31") # True even though April has only 30 days.  True   '''  # Algorithm: Check length, then pull pieces apart and check them. Use only  # basic string  # manipulation, comparisons, and type conversion. Please do not use any  # powerful date functions  # you may find in python libraries.  # 2015-10-12  # 0123456789   # YOUR CODE GOES HERE  pass def is_natural_number(str): '''  (str) -> bool  Return whether str is a string representation of a natural number,  that is, 0,1,2,3,...,23,24,...1023, 1024, ...  In CS, 0 is a natural number  param str: string  return: True if num is a string consisting of only digits. False otherwise.  Example:   >>> is_natural_number("0")  True  >>> is_natural_number("05")  True  >>> is_natural_number("2015")  True  >>> is_natural_number("9 3")  False  >>> is_natural_number("sid")  False  >>> is_natural_number("2,192,134")  False   '''  # Algorithm:  # Check that the string has length > 0  # Check that all characters are in ["0123456789"]   # YOUR CODE GOES HERE  pass def parse_command(line): '''  (str) -> list  Parse command and arguments from the line. Return a list  [command, arg1, arg2, ...]  Return ["error", ERROR_DETAILS] if the command is not valid.  Return ["help"] otherwise.  The valid commands are   1) add DATE DETAILS  2) show  3) delete DATE NUMBER  4) quit  5) help   line: a string command  return: A list consiting of [command, arg1, arg2, ...].  Return ["error", ERROR_DETAILS], if  line can not be parsed.   Example:  >>> parse_command("add 2015-10-21 budget meeting")  ['add', '2015-10-21', 'budget meeting']  >>> parse_command("")  ['help']  >>> parse_command("not a command")  ['help']  >>> parse_command("help")  ['help']  >>> parse_command("add")  ['error', 'add DATE DETAILS']  >>> parse_command("add 2015-10-22")  ['error', 'add DATE DETAILS']  >>> parse_command("add 2015-10-22 Tims with Sally.")  ['add', '2015-10-22', 'Tims with Sally.']  >>> parse_command("add 2015-10-35 Tims with Sally.")  ['error', 'not a valid calendar date']  >>> parse_command("show")  ['show']  >>> parse_command("show calendar")  ['error', 'show']  >>> parse_command("delete")  ['error', 'delete DATE NUMBER']  >>> parse_command("delete 15-10-22")  ['error', 'delete DATE NUMBER']  >>> parse_command("delete 15-10-22 1")  ['error', 'not a valid calendar date']  >>> parse_command("delete 2015-10-22 3,14")  ['error', 'not a valid event index']  >>> parse_command("delete 2015-10-22 314")  ['delete', '2015-10-22', '314']  >>> parse_command("quit")  ['quit']   '''  # HINT: You can first split, then join back the parts of  # the final argument.  # YOUR CODE GOES HERE  pass if __name__ == "__main__": import doctest doctest.testmod()