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我想写一个函数：

match_string(input, pattern, valid_words, date_format)

input是一个普通的字符串。pattern是一个字符串，其中包含数字、单词和日期的占位符。例如，“# 是数字 ## 是字符串，### 是日期”。在这里，我使用#、# 和### 分别表示数字、字符串和日期占位符，但我不受占位符的任何特定表示形式的约束。

match_string如果input“匹配”模式，则应返回 true；也就是说，如果它有数字，其中有数字占位符，单词有单词占位符并且单词在给定的 valid_words 列表中，以及日期有日期占位符并且日期在给定的date_format.

最后我需要 match_string 来返回详细的错误信息；如果input不匹配，并且它是占位符之一，它应该说“不是数字”、“不在单词列表中”或“不是日期”。如果它与模式的正常部分不匹配，它应该只是错误或返回 False

这是很多要问的:) 但问题是如何实施match_string。我看到正则表达式和字符串格式以及自定义错误定义应该对我有所帮助，但我无法将它们全部放在一起。我希望这个问题可以通过在 python 中灵活使用正则表达式来帮助其他人。

例子：

> match_string('1 is a number foo is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', [foo], '%m-%d-%y')
True

> match_string('foo is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', [foo], '%m-%d-%y')
Error: number expected for 'foo'

> match_string('1 is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', [foo], '%m-%d-%y')
Error: invalid word: bar

> match_string('1 is a number foo is a string January is a date', '# is a number ## is a string ### is a date', [foo], '%m-%d-%y')
Error: invalid date format January

提前致谢！

4

1 回答 1

2

我认为直接操作字符串或仅修改单个正则表达式模式会更有效。不幸的是，后者只会返回真或假。

无论如何，我根据要求创建了一个脚本，虽然它会接受每个月的 31 天，但添加更多限制应该相当容易。

from re import sub, match

def match_string(input, pattern, valid_words, date_format):
    errors = []

    # makes sure that input and pattern are compatible
    regex_pattern = sub(r'#{1,3}', '(.+?)', pattern)
    if not match(regex_pattern, input):
        return 'Error: Input doesn\'t match pattern!'   

    # converts the data_format to a regex
    date_regex = sub(r'%d', '(?P<day>\d+)', date_format)
    date_regex = sub(r'%m', '(?P<month>\d+)', date_regex)
    date_regex = sub(r'%y', '(?P<year>\d+)', date_regex)

    # extracts the dates
    regex_pattern = sub(r'###', '(.+?)', pattern)
    regex_pattern = sub(r'##', '(?:.+?)', regex_pattern)
    regex_pattern = sub(r'#', '(?:.+?)', regex_pattern)
    for date in match(regex_pattern, input).groups():
        m = match(date_regex, date)
        if not m:
            errors.append('Error: %s is not a valid date!' % date)
        else:
            if int(m.group('day')) < 1 or 31 < int(m.group('day')):
                errors.append('Error: %s is not a valid day!' % m.group('day'))
            if int(m.group('month')) < 1 or 12 < int(m.group('month')):
                errors.append('Error: %s is not a valid month!' % m.group('month'))

    # extracts the generic words
    regex_pattern = sub(r'###', '(?:.+?)', pattern)
    regex_pattern = sub(r'##', '(.+?)', regex_pattern)
    regex_pattern = sub(r'#', '(?:.+?)', regex_pattern)
    for word in match(regex_pattern, input).groups():
        if not word.strip() in valid_words:
            errors.append('Error: %s is not a valid word!' % word)

    # extracts the numbers
    regex_pattern = sub(r'###', '(?:.+?)', pattern)
    regex_pattern = sub(r'##', '(?:.+?)', regex_pattern)
    regex_pattern = sub(r'#', '(.+?)', regex_pattern)
    for number in match(regex_pattern, input).groups():
        if not match(r'\d+', number):
            errors.append('Error: %s is not a valid number!' % number)

    if len(errors) == 0:
        return True
    else:
        return '\n'.join(errors)

print match_string('1 and 2 are numbers foo and bar are strings 12-1-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
print
print match_string('1 is a number foo is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
print
print match_string('foo is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
print
print match_string('1 is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
print
print match_string('1 is a number foo is a string January is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')

产生结果：

True

True

Error: bar is not a valid word!
Error: foo is not a valid number!

Error: bar is not a valid word!

Error: January is not a valid date!

如您所见，您的第二个示例有两个错误，而不是一个。

编辑：

我在不使用正则表达式的情况下重新制作了程序。它应该更有效率。看起来它只遍历输入一次，但它仍然使用startswith() 方法多次读取一些字符。

此版本在检测到错误时立即返回。因此它只会检测每个输入的第一个错误。

def match_string(input, pattern, valid_words, date_format):
    print '\n> match_string(\'%s\', \'%s\', %s, \'%s\')' % (input, pattern, valid_words, date_format)

    digits = '0123456789'
    inputIndex = 0
    patternIndex = 0

    while inputIndex < len(input) and patternIndex < len(pattern):
        if pattern[patternIndex] == '#':
            patternIndex += 1
            if pattern[patternIndex] == '#':
                patternIndex += 1
                if pattern[patternIndex] == '#':

                    # validate date
                    date_formatIndex = 0
                    while inputIndex < len(input) and date_formatIndex < len(date_format):

                        if input[inputIndex] == date_format[date_formatIndex]:
                            inputIndex += 1
                            date_formatIndex += 1

                        elif input[inputIndex] in digits:

                            startIndex = inputIndex
                            while inputIndex < len(input) and input[inputIndex] in digits:
                                inputIndex += 1
                            number = int(input[startIndex:inputIndex])

                            if date_format[date_formatIndex:].startswith('%y'):
                                placeholder = True
                            elif date_format[date_formatIndex:].startswith('%m'):
                                if number < 1 or 12 < number:
                                    return 'Error: expected a month between 1 and 12\n input   %d -> "...%s"\n pattern %d -> "...%s"\n date format %d -> "...%s"' % (startIndex, input[startIndex:], patternIndex - 2, pattern[patternIndex - 2:], date_formatIndex, date_format[date_formatIndex:])   

                            elif date_format[date_formatIndex:].startswith('%d'):
                                if number < 1 or 31 < number:
                                    return 'Error: expected a day between 1 and 31\n input   %d -> "...%s"\n pattern %d -> "...%s"\n date format %d -> "...%s"' % (startIndex, input[startIndex:], patternIndex - 2, pattern[patternIndex - 2:], date_formatIndex, date_format[date_formatIndex:])   

                            else:
                                return 'Error: input doesn\'t match date format\n input   %d -> "...%s"\n pattern %d -> "...%s"\n date format %d -> "...%s"' % (startIndex, input[startIndex:], patternIndex - 2, pattern[patternIndex - 2:], date_formatIndex, date_format[date_formatIndex:])   

                            date_formatIndex += 2

                        else:
                            return 'Error: input doesn\'t match date format\n input   %d -> "...%s"\n pattern %d -> "...%s"\n date format %d -> "...%s"' % (inputIndex, input[inputIndex:], patternIndex - 2, pattern[patternIndex - 2:], date_formatIndex, date_format[date_formatIndex:])   

                    patternIndex += 1

                else:
                    # validate word
                    valid = False
                    for word in valid_words:
                        if input[inputIndex:].startswith(word):
                            valid = True
                            inputIndex += len(word)
                            break
                    if not valid:
                        return 'Error: expected a valid word\n input   %d -> "...%s"\n pattern %d -> "...%s"' % (inputIndex, input[inputIndex:], patternIndex - 2, pattern[patternIndex - 2:])                    

            else:
                # validate number
                if not input[inputIndex] in digits:
                    return 'Error: expected a number\n input   %d -> "...%s"\n pattern %d -> "...%s"' % (inputIndex, input[inputIndex:], patternIndex - 1, pattern[patternIndex - 1:])
                while inputIndex < len(input) and input[inputIndex] in digits:
                    inputIndex += 1

        elif input[inputIndex] != pattern[patternIndex]:
            return 'Error: input and pattern do not match\n input   %d -> "...%s"\n pattern %d -> "...%s"' % (inputIndex, input[inputIndex:], patternIndex, pattern[patternIndex:])
        else:
            inputIndex += 1            
            patternIndex += 1
    return True

print match_string('1 and 2 are numbers foo and bar are strings 12-1-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
print match_string('1 is a number foo is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
print match_string('foo is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
print match_string('1 is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
print match_string('1 is a number foo is a string January is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
print match_string('1 and 2 are numbers foo and bar are strings 15-1-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
print match_string('1 and 2 are numbers foo and bar are strings 08-42-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
print match_string('1 and 2 are numbers foo and bar are strings 08;4;2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
print match_string('1 and 2 are numbers foo and bar are strings 08-4-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '~%m-%d-%y')

产生结果（我添加了更多测试）：

> match_string('1 and 2 are numbers foo and bar are strings 12-1-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
True

> match_string('1 is a number foo is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
True

> match_string('foo is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
Error: expected a number
 input   0 -> "...foo is a number bar is a string 12-1-2013 is a date"
 pattern 0 -> "...# is a number ## is a string ### is a date"

> match_string('1 is a number bar is a string 12-1-2013 is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
Error: expected a valid word
 input   14 -> "...bar is a string 12-1-2013 is a date"
 pattern 14 -> "...## is a string ### is a date"

> match_string('1 is a number foo is a string January is a date', '# is a number ## is a string ### is a date', ['foo'], '%m-%d-%y')
Error: input doesn't match date format
 input   30 -> "...January is a date"
 pattern 29 -> "...### is a date"
 date format 0 -> "...%m-%d-%y"

> match_string('1 and 2 are numbers foo and bar are strings 15-1-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
Error: expected a month between 1 and 12
 input   44 -> "...15-1-2013 is a date"
 pattern 42 -> "...### is a date"
 date format 0 -> "...%m-%d-%y"

> match_string('1 and 2 are numbers foo and bar are strings 08-42-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
Error: expected a day between 1 and 31
 input   47 -> "...42-2013 is a date"
 pattern 42 -> "...### is a date"
 date format 3 -> "...%d-%y"

> match_string('1 and 2 are numbers foo and bar are strings 08;4;2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '%m-%d-%y')
Error: input doesn't match date format
 input   46 -> "...;4;2013 is a date"
 pattern 42 -> "...### is a date"
 date format 2 -> "...-%d-%y"

> match_string('1 and 2 are numbers foo and bar are strings 08-4-2013 is a date', '# and # are numbers ## and ## are strings ### is a date', ['foo', 'bar'], '~%m-%d-%y')
Error: input doesn't match date format
 input   44 -> "...08-4-2013 is a date"
 pattern 42 -> "...### is a date"
 date format 0 -> "...~%m-%d-%y"
于 2013-08-25T10:49:51.777 回答