《Python3程序开发指南（第二版）》第2章 数据类型 练习

1.修改程序print_unicode.py，以便用户可以在命令行上输入几个单独的单词，并且只有在Unicode字符名包含用户所指定的所有单词时才打印相应列。

__author__ = 'Ibuki Suika'import sysimport unicodedatadef print_unicode_table(words):    print("decimal   hex   chr  {0:^40}".format("name"))    print("-------  -----  ---  {0:-<40}".format(""))    code = ord(" ")    end = min(0xD800, sys.maxunicode)    while code < end:        c = chr(code)        name = unicodedata.name(c, "*** unknown ***")        b = True        for word in words:            if word.lower() not in name.lower():                b = False                break        if b:            print("{0:7}  {0:5X}  {0:^3c}  {1}".format(code, name.title()))        code += 1words = []if len(sys.argv) > 1:    if sys.argv[1] in ("-h", "--help"):        print("usage: {0} [string]".format(sys.argv[0]))        word = None    else:        words = sys.argv[1:]if words is not None:    print_unicode_table(words)

2.修改quadratic.py，使得系数0.0对应的方程项不再输出，负数系数的输出形式为-n，而不是+-n。

__author__ = 'Ibuki Suika'import cmathimport mathimport sysdef get_float(msg, allow_zero):    x = None    while x is None:        try:            x = float(input(msg))            if not allow_zero and abs(x) < sys.float_info.epsilon:                print("zero is not allowed")                x = None        except ValueError as err:            print(err)    return xprint("ax\N{SUPERSCRIPT TWO} + bx + c = 0")a = get_float("enter a: ", False)b = get_float("enter b: ", True)c = get_float("enter c: ", True)x1 = Nonex2 = Nonediscriminant = (b ** 2) - (4 * a * c)if discriminant == 0:    x1 = -(b / (2 * a))else:    if discriminant > 0:        root = math.sqrt(discriminant)    else:        root = cmath.sqrt(discriminant)    x1 = (-b + root) / (2 * a)    x2 = (-b - root) / (2 * a)equation = "{0}x\N{SUPERSCRIPT TWO}".format(a)if b != 0:    equation += "{0:+}x".format(b)if c != 0:    equation += "{0:+}".format(c)equation += "=0 \N{RIGHTWARDS ARROW} x = {0}".format(x1)if x2 is not None:    equation += " or x = {0}".format(x2)print(equation)

3.从csv2html.py程序中删除escape_html()函数，使用xml.sax.saxutils模块中的xml.sax.saxutils.escape() 函数替代地完成相关功能。

__author__ = 'Ibuki Suika'import sysfrom xml.sax.saxutils import escapedef main():    maxwidth = 100    print_start()    count = 0    while True:        try:            line = input()            if count == 0:                color = "lightgreen"            elif count % 2:                color = "white"            else:                color = "lightyellow"            print_line(line, color, maxwidth)            count += 1        except EOFError:            break    print_end()def print_start():    print("<table border='1'>")def print_line(line, color, maxwidth):    print("<tr bgcolor='{0}'>".format(color))    fields = extract_fields(line)    for field in fields:        if not field:            print("<td></td>")        else:            number = field.replace(",", "")            try:                x = float(number)                print("<td align='right'>{0:d}</td>".format(round(x)))            except ValueError:                field = field.title()                field = field.replace(" And ", " and ")                if len(field) <= maxwidth:                    field = escape(field)                else:                    field = "{0} ...".format(escape(field[:maxwidth]))                print("<td>{0}</td>".format(field))    print("</tr>")def extract_fields(line):    fields = []    field = ""    quote = None    for c in line:        if c in "\"'":            if quote is None: # start of quoted string                quote = c            elif quote == c:  # end of quoted string                quote = None            else:                field += c    # other quote inside quoted string            continue        if quote is None and c == ",": # end of a field            fields.append(field)            field = ""        else:            field += c        # accumulating a field    if field:        fields.append(field)  # adding the last field    return fieldsdef print_end():    print("</table>")main()

4.再次对csv2html.py进行修改，这次要求添加一个名为process_options()的新函数。这一函数应该从main()中进行调用，并返回一个两元组：maxwidth(int型)和format(str型)。

import sysimport xml.sax.saxutilsdef main():    maxwidth, format = process_options()    if maxwidth is not None:        print_start()        count = 0        while True:            try:                line = input()                if count == 0:                    color = "lightgreen"                elif count % 2:                    color = "white"                else:                    color = "lightyellow"                print_line(line, color, maxwidth, format)                count += 1            except EOFError:                break        print_end()def process_options():    maxwidth_arg = "maxwidth="    format_arg = "format="    maxwidth = 100    format = ".0f"    for arg in sys.argv[1:]:        if arg in ["-h", "--help"]:            print("""\usage:csv2html.py [maxwidth=int] [format=str] < infile.csv > outfile.htmlmaxwidth is an optional integer; if specified, it sets the maximumnumber of characters that can be output for string fields,otherwise a default of {0} characters is used.format is the format to use for numbers; if not specified itdefaults to "{1}".""".format(maxwidth, format))            return None, None        elif arg.startswith(maxwidth_arg):            try:                maxwidth = int(arg[len(maxwidth_arg):])            except ValueError:                pass        elif arg.startswith(format_arg):            format = arg[len(format_arg):]    return maxwidth, formatdef print_start():    print("<table border='1'>")def print_line(line, color, maxwidth, format):    print("<tr bgcolor='{0}'>".format(color))    numberFormat = "<td align='right'>{{0:{0}}}</td>".format(format)    fields = extract_fields(line)    for field in fields:        if not field:            print("<td></td>")        else:            number = field.replace(",", "")            try:                x = float(number)                print(numberFormat.format(x))            except ValueError:                field = field.title()                field = field.replace(" And ", " and ")                if len(field) <= maxwidth:                    field = xml.sax.saxutils.escape(field)                else:                    field = "{0} ...".format(                            xml.sax.saxutils.escape(field[:maxwidth]))                print("<td>{0}</td>".format(field))    print("</tr>")def extract_fields(line):    fields = []    field = ""    quote = None    for c in line:        if c in "\"'":            if quote is None:                quote = c            elif quote == c:                quote = None            else:                field += c            continue        if quote is None and c == ",":            fields.append(field)            field = ""        else:            field += c    if field:        fields.append(field)    return fieldsdef print_end():    print("</table>")main()