Regular Expressions Patterns
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Questions and Answers

What is the purpose of the \b anchor in regular expressions?

  • To match a word boundary (correct)
  • To match a whitespace character
  • To match a digit
  • To match the start of a string
  • What is the difference between a capturing group and a non-capturing group in regular expressions?

  • A capturing group matches more characters than a non-capturing group
  • A capturing group is used for quantifiers, while a non-capturing group is used for anchors
  • A capturing group is used for positive lookahead, while a non-capturing group is used for negative lookahead
  • A capturing group remembers the match, while a non-capturing group does not (correct)
  • What is the purpose of the (?:abc) syntax in regular expressions?

  • To create a non-capturing group (correct)
  • To match the string 'abc' exactly
  • To create a capturing group
  • To match the string 'abc' in a case-insensitive manner
  • What does the quantifier a{1,3} match in regular expressions?

    <p>Between one and three 'a' characters</p> Signup and view all the answers

    What is the purpose of the \W character class in regular expressions?

    <p>To match a non-word character</p> Signup and view all the answers

    What does the character class [a-g] match in regular expressions?

    <p>any character between a and g</p> Signup and view all the answers

    What is the purpose of the character in regular expressions?

    <p>to match a tab character</p> Signup and view all the answers

    What does the regular expression a{2,} match?

    <p>two or more a's</p> Signup and view all the answers

    What is the purpose of the (?=abc) syntax in regular expressions?

    <p>to match abc without including it in the match</p> Signup and view all the answers

    What does the regular expression a+?a{2,}? match?

    <p>as few a's as possible, followed by two or more a's</p> Signup and view all the answers

    Study Notes

    Character Classes

    • Any character except newline: \w, \d, \s match word, digit, whitespace respectively
    • Not word, digit, whitespace: \W, \D, \S respectively
    • Match any of a, b, or c: [abc]
    • Not a, b, or c: [^abc]
    • Character between a & g: [a-g]

    Anchors

    • Start of the string: ^
    • End of the string: $
    • Word boundary: \b
    • Not-word boundary: \B

    Escaped Characters

    • Escaped special characters: \., \\
    • Tab, linefeed, carriage return: \t, \n, \r

    Groups & Lookaround

    • Capture group: (abc)
    • Backreference to group #1: \1
    • Non-capturing group: (?:abc)
    • Positive lookahead: (?=abc)
    • Negative lookahead: (?!abc)

    Quantifiers & Alternation

    • 0 or more, 1 or more, 0 or 1: a*, a+, a?
    • Exactly five, two or more: a{5}, a{2,}
    • Between one & three: a{1,3}
    • Match as few as possible: a+?, a{2,}?
    • Match ab or cd: ab|cd

    Character Classes

    • Any character except newline: \w, \d, \s match word, digit, whitespace respectively
    • Not word, digit, whitespace: \W, \D, \S respectively
    • Match any of a, b, or c: [abc]
    • Not a, b, or c: [^abc]
    • Character between a & g: [a-g]

    Anchors

    • Start of the string: ^
    • End of the string: $
    • Word boundary: \b
    • Not-word boundary: \B

    Escaped Characters

    • Escaped special characters: \., \\
    • Tab, linefeed, carriage return: \t, \n, \r

    Groups & Lookaround

    • Capture group: (abc)
    • Backreference to group #1: \1
    • Non-capturing group: (?:abc)
    • Positive lookahead: (?=abc)
    • Negative lookahead: (?!abc)

    Quantifiers & Alternation

    • 0 or more, 1 or more, 0 or 1: a*, a+, a?
    • Exactly five, two or more: a{5}, a{2,}
    • Between one & three: a{1,3}
    • Match as few as possible: a+?, a{2,}?
    • Match ab or cd: ab|cd

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    Description

    Test your understanding of character classes, anchors, and groups in regular expressions. Learn to match patterns and create efficient regex expressions.

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