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Regular Expressions Tutorial: Diving into Python Ch.7 Number Systems Election of Class Representative

This tutorial covers regular expressions and number systems, with a focus on the election of a class representative. Duties include representing the interests of the class at departmental meetings and on an ad-hoc basis. The tutorial also includes mini-tests and a revision exercise.

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Regular Expressions Tutorial: Diving into Python Ch.7 Number Systems Election of Class Representative

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  1. CSC1018F:Regular Expressions(Tutorial) Diving into Python Ch. 7 Number Systems

  2. Election of Class Representative • Duties: • Represent the interests and concerns of the class • At regular departmental meetings • On an ad-hoc basis • This does not mean that individuals cannot approach the tutors, TA, course coordinator or lecturer

  3. Mini-Test Answers (1) • The regular expression r"^(\d{3})\D*(\d{4})\D+$" will match successfully to: • "1234567" • "123-4567abc" • "1234567x" • "12345678" • "/1234567/" • A regular expression which accepts names of the type (Mr Warren Worthington) prefixed by the designation (Mr, Mrs, Ms, Dr, Prof) with a single first name and single surname and that groups the components of the name, will have the form: • r"\bMr|Mrs|Ms|Dr|Prof \D+ \D+%” • "\b(Mr|Mrs|Ms|Dr|Prof)\D([A-Z][a-z])\D([A-Z][a-z])%” • r"^(M\D+|Dr|Prof) (\D+) (\D+|\D+-\D+)%” • r"^(Mr|Mrs|Ms|Dr|Prof) ([A-Z][a-z]*) ([A-Z][a-z]*)%” (Where [a-z] expresses a range of possible single characters)

  4. Mini-Test Answers (2) • The binary number 101010 has a hexadecimal representation of: • 2A • 222 • A2 • CA • The The hexadecimal number BED has a binary representation of: • 011101111111 • 101111101101 • 111101110111 • 111111011110

  5. Mini-Test Answers (3) • Construct a regular expression that will parse land-line telephone numbers. • Regional code is a 0 followed by two or three digits. Land-line codes may have an optional international prefix of “+27” in which case the zero prefix and parentheses fall away (e.g., “+2721”). The local dialling code can have five or six numeric digits. • r"^((\+27\d{2,3})|(\(0\d{2,3}\))) \d{6,7}$"

  6. Revision Exercise • Create a function which will take a date string in any one of the following formats: • dd/mm/yyyy or dd/mm/yy • Other separators (e.g., ‘\’, ‘ ‘, ‘-’) are also allowed • Single figure entries may have the form x or 0x, e.g. 3/4/5 or 03/04/05 • dd month yy or yyyy where month may be written in full (December) or abbreviated (Dec. or Dec) • And return it in the format: • dd month(in full) yyyy, e.g. 13 March 2006 • Implement this using regular expressions and also implement range checking on dates

  7. Revision Solution (1) def parseDate(dateStr): import re monthRange = (31, 28, 31, 30, 31, 30, 31, 31, 30, … monthName = ("January", "February", … monthAbbr = ["Jan", "Feb", "Mar", "Apr", "May", … # Parsing datePattern = r"""^ (\d{1,2}) # day (1 or 2 digits) \W+ # any non-alphanumeric separator (\d{1,2} | # month (1 or 2 digits) January | February | March | April | May | June | July | August | September | October | November | December | # month in full Jan.? | Feb.? | Mar.? | Apr.? | May.? | Jun.? | Jul.? | Aug.? | Sep.? | Oct.? | Nov.? | Dec.?) # abbreviated month \W+ # any non-alphanumeric separator (\d{1,2} | \d{4}) # year (1, 2 or 4 digits) $ """

  8. Revision Solution (2) resDate = re.search(datePattern, dateStr, re.VERBOSE) if resDate == None: return None else: # find month entry resTuple = resDate.groups() day = resTuple[0] month = resTuple[1] year = resTuple[2] try: monthInd = int(month)-1 except ValueError: # match on first 3 chars of month monthInd = monthAbbr.index(month[:3]) if int(day) < 1 or int(day) > monthRange[monthInd]: return None else: if len(year) == 2: # fix year if needed year = int(year) > 50 and "19" + year or "20" + year return str(int(day)) + " " + monthName[monthInd] + " " + year

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