RegEx

Question 2

What does the caret symbol (^) signify in a regular expression?

Answer 2

It signifies the start of a string.

Question 3

What does the dollar sign symbol ($) signify in a regular expression?

Answer 3

It signifies the end of a string.

Question 4

True or False: The dot (.) in a regular expression matches any single character except newline characters.

Answer 4

True.

Question 5

What does the asterisk (*) symbol do in a regular expression?

Answer 5

It matches zero or more occurrences of the preceding element.

Question 6

Fill in the blank: The plus sign (+) matches _____ occurrences of the preceding element.

Answer 6

one or more.

Question 7

Which escape character is used to match special characters in a regular expression?

Answer 7

The backslash (\) is used to escape special characters in regular expressions.

For example, to match a literal period (.) instead of the “any character” wildcard, you’d write \.. Similarly, \* matches a literal asterisk, \? matches a literal question mark, and so on.Backslash ().

Question 8

What is the purpose of parentheses () in a regular expression?

Answer 8

They are used to group expressions and capture matched substrings. A part of a regular expression that is enclosed in parentheses (subexpression) counts as a single element as far as the operators following it are concerned.

Question 9

What does the question mark (?) signify in a regular expression?

Answer 9

It makes the preceding element optional, matching zero or one occurrence.

Question 10

True or False: The curly braces ({}) are used to specify the exact number of occurrences of a preceding element.

Answer 10

True.

Question 11

What does the expression [abc] match?

Answer 11

It matches any single character ‘a’, ‘b’, or ‘c’.

Question 12

What does the expression [^abc] match?

Answer 12

It matches any single character except ‘a’, ‘b’, or ‘c’.

Question 13

Multiple choice: Which of the following is a valid way to match a digit in a regular expression?

Answer 13

\d

Question 14

What does the expression \D match?

Answer 14

It matches any character that is not a digit.

Question 15

Fill in the blank: The expression \s matches any _____ character.

Answer 15

whitespace.

Question 16

What does the expression \S match?

Answer 16

It matches any character that is not a whitespace.

Question 17

What does the expression \w match?

Answer 17

It matches any word character (alphanumeric plus underscore).

Question 18

What does the expression \W match?

Answer 18

It matches any character that is not a word character.

Question 19

True or False: The vertical bar (|) is used to denote alternation in regular expressions.

Answer 19

True.

Question 20

What is the purpose of the ‘g’ flag in a regular expression?

Answer 20

It signifies a global search, finding all matches rather than stopping after the first.

Question 21

What does the ‘i’ flag do in a regular expression?

Answer 21

It makes the search case-insensitive.

Question 22

What is the purpose of the ‘m’ flag in a regular expression?

Answer 22

It allows the caret (^) and dollar sign ($) to match the start and end of each line in a multiline string.

Question 23

What is this a regex pattern for?
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,}

Answer 23

email address

Question 24

What does the expression {n,m} specify in a regular expression?

Answer 24

It matches between n and m occurrences of the preceding element.

Question 25

Fill in the blank: The expression (?i) at the beginning of a regex pattern makes the entire pattern _____-sensitive.

Answer 25

case.

Question 26

What does the expression (?P...) do in a regular expression?

Answer 26

It creates a named group for capturing. pattern = r"(?P\d{3})-(?P\d{3})-(?P\d{4})" match = re.search(pattern, "555-123-4567") print(match.group("area_code")) # 555 print(match.group("exchange")) # 123 print(match.group("number")) # 4567

Question 27

True or False: Regular expressions can be used for string substitution.

Answer 27

True. (using .replace())

Question 28

exec method

Answer 28

Regular expressions also have an exec (execute) method that will return null if no match was found and return an object with information about the match otherwise. let match = /\d+/.exec("one two 100"); console.log(match); // → ["100"] console.log(match.index); // → 8

Question 29

/i

Answer 29

let cartoonCrying = /boo+(hoo+)+/i; i = "ignore case"

Question 30

\b

Answer 30

The \b marker matches word boundaries, positions that have a word character on one side, and a nonword character on the other.

Question 31

look-ahead

Answer 31

(?=...) is a positive lookahead: It checks that a pattern follows but doesn’t consume it (doesn’t include it in the match). (?!...) is a negative lookahead: It checks that a pattern does NOT follow, without consuming characters. Practical use case — matching without including javascript "100px 200em 300px".match(/\d+(?=px)/g) // → ["100", "300"] You want the numbers, but only those followed by px. The px is checked but not included in the result. If you did consume it: javascript "100px 200em 300px".match(/\d+px/g) // → ["100px", "300px"] // Now px is part of the match

Question 32

choice pattern

Answer 32

The pipe character (|) denotes a choice between the pattern to its left and the pattern to its right.

Question 33

/g

Answer 33

When a g option (for global) is added after the regular expression, all matches in the string will be replaced, not just the first. console.log("Borobudur".replace(/[ou]/, "a")); // → Barobudur console.log("Borobudur".replace(/[ou]/g, "a")); // → Barabadar

Question 34

greed

Answer 34

The repetition operators (+, *, ?, and {}) are greedy, meaning they match as much as they can and backtrack from there. If you put a question mark after them (+?, *?, ??, {}?), they become nongreedy and start by matching as little as possible, matching more only when the remaining pattern does not fit the smaller match.