python coding error

[isntitzee]

#!/usr/bin/env python3
#The leap_year() function will take a year in "YYYY" format, and return True if the given year is a leap year, otherwise return False.
The range_check() function will take an integer object and a tuple with two integer values, the first value indicates the lower bound and the second one indicates the upper bound of a integer range. If the integer object falls in between the range given in the tuple, return 'True', otherwise return 'False'.
The sanitize() function will take two string objects, the first string object is the object to be sanitized, and the 2nd string object contains letters that are allowed. This function will return the first object with letters not in the 2nd string object removed.
The size_check() function will take an collection data type object and expected number of items as an integer and will return either 'True' or 'False'. If the number of items in the data object match the integer value given, return 'True', otherwise return 'False'
The usage() function will take no argument and return a string describing the usage of the script.
# Imports the sys module
import sys

# usage function
# Shows the user how they should use the program properly
def usage():
    '''
    Help on function usage in module a1_szrahman3:

    leap_year() prints out an error message if an error has occured
    e.g. usage() -> 'Usage: a1_szrahman3 [--step] YYYYMMDD|YYYY/MM/DD|YYYY-MM-DD|YYYY.MM.DD +/-n'
    (END)
    '''
    return "Usage: a1_szrahman3.py [--step] YYYYMMDD|YYYY/MM/DD|YYYY-MM-DD|YYYY.MM.DD|YYYY/MM/DD|YYYY-MM-DD|YYYY.MM.DD +/-n"

# range_check function
# It goes through an exception checking
# whether or not its ran properly or not
# If the arguments were not given properly
# it calls the usage function
# Otherwise it goes to a loop where it calls
# Either the tomorrow, or the yesterday function
def range_check(date, day):
    """
    Help on function range_check in module a1_szrahman3:

    range_check(date, day) -> str/int
    range_check(date, day) takes YYYYMMDD|YYYY/MM/DD|YYYY-MM-DD|YYYY.MM.DD|YYYY/MM/DD|YYYY-MM-DD|YYYY.MM.DD and a positive or negative interger to
    call the other functions in order to do the
    calculations, while also calling size_check to determine if the date
    is valid or not.
    e.g. range_check(20200320, 5) -> 20200325
         range_check(20200320, -5) -> 20200315
    (END)
    """
    error = usage()
    if len(date) != 8:
        return "Error 09: wrong date entered"
        sys.exit()
    try:
        num = int(day)
        tmpdate = date
        valid = size_check(date)
        if valid == False:
            sys.exit()
        else:
            while num != 0:
                if num > 0:
                    tmpdate = tomorrow(tmpdate)
                    num = num - 1
                else:
                    tmpdate = yesterday(tmpdate)
                    num = num + 1
        error = usage()
        tar = tmpdate
        return tar
    except ValueError:
        return error






# sanitize function
# While it also checks if it is a leap year
# It also stores the max day in a tuple
def sanitize(tmp_year):
    """
    Help on function sanitize in module a1_szrahman3:

    sanitize(tmp_year) -> int
    sanitize() takes the year and calls the
    leap_year function which will determine the ,
    max number of days for February
    e.g: sanitize(2020) -> 2:29
         sanitize(2019) -> 2:28
    (END)
    """
    leapyear = tmp_year
    check = leap_year(leapyear)

    if check == True:
        febmax = 29
    elif check == False:
        febmax =28

    month_max = {1: 31, 2: febmax, 3: 31, 4: 30, 5: 31, 6: 30, 7: 31, 8: 31,
                 9: 30, 10: 31, 11: 30, 12: 31}

    return month_max

# leap_year function
# Check if year is leapyear
# If it is, returns as True
# If not, returned as False
def leap_year(leap):
    """
    Help on function leap_year in module a1_szrahman3:

    leap_year(leap) -> int
    leap_year() determines if the year is a leap year
    which will return as True or False
    e.g: leap_year(2020) -> True
         leap_year(2019) -> False
    (END)
    """
    l_year = leap
    if l_year % 4 == 0:
        return True
    elif l_year % 100 == 0:
        return False
    elif l_year % 400 == 0:
        return True
    else:
        return False

# size_check function
# Strips the variable
# Then runs through
# Statements to see if valid
# If valid, returns as True
# If not, calls one of the functions to
# Print out the error
# While elso returning a False Statement
def size_check(date):
    """
    Help on function size_check in module a1_szrahman3:

    size_check(date) -> str
    size_check() determines if the date given is a valid date
    or not, which returns True or False (which also prints out a message)
    e.g: size_check(20200314) -> True
         size_check(20200231) -> False -> 'Error 03: wrong day entered'
         size_check(20201324) -> False -> 'Error 02: wrong month entered'
    (END)
    """
    y = int(date[0:4])
    m = int(date[4:6])
    d = int(date[6:])
    tmp_d = d
    tmp_m = m
    sanitize = sanitize(y)
    if tmp_m > 12 or tmp_m < 1:
        print("Error 02: wrong month entered")
        return False
    else:
        if tmp_d > sanitize[m]:
            print("Error 03: wrong day entered")
            return False
        else:
            return True

if __name__ == "__main__":
    if len(sys.argv) == 3:
        d = sys.argv[1]
        n = sys.argv[2]
        steparg = False
        print(range_check(d, n))
    elif len(sys.argv) == 4:
        s = sys.argv[1]
        d = sys.argv[2]
        n = sys.argv[3]
        if s == "--step":
            steparg = True
            range_check(d, n)
        else:
            print(usage())
    else:
        print((usage()))

[buran]

Please, use proper tags when post code, traceback, output, etc. This time I have added tags for you.
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