REGular EXpressions from HackerRank (with Solutions in Python 3)

Highlighted part in the Test String is matched with regex pattern.

Introduction

1. Matching Specific String

Regex Pattern - wikipedia

Test String - https://en. wikipedia .org/

Regex_Pattern = r'hackerrank'	# Do not delete 'r'.

import re
Test_String = input()
match = re.findall(Regex_Pattern, Test_String)
print("Number of matches :", len(match))

2. Matching Anything But a Newline

dot - The dot (.) matches anything (except for a newline).

Regex Pattern - A.B.C.D.

Test String - A+B+C=DE

regex_pattern = r"^...\....\....\....$"	# Do not delete 'r'.

import re
import sys
test_string = input()
match = re.match(regex_pattern, test_string) is not None
print(str(match).lower())

3. Matching Digits & Non-Digit Characters

\d - The expression \d matches any digit [0-9].

\D - The expression \D matches any character that is not a digit.

Regex Pattern - \D\D\D\D

Test String - Hack101

Regex_Pattern = r"\d\d\D\d\d\D\d\d\d\d"	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

4. Matching Whitespace & Non-Whitespace Character

\s - \s matches any whitespace character [ \r\n\t\f ].

\S - \S matches any non-white space character.

Regex Pattern - \s

Test String - A B

Regex_Pattern = r"\S\S\s\S\S\s\S\S"	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

5. Matching Whitespace & Non-Whitespace Character

\w - The expression \w will match any word character. Word characters include alphanumeric characters (a-z, A-Z and 0-9) and underscores ( _ ).

\W - \W matches any non-word character. Non-word characters include characters other than alphanumeric characters (a-z, A-Z and 0-9) and underscore ( _ ).

Regex Pattern - \w\w\w

Test String - $one

Regex_Pattern = r"\w\w\w\W\w\w\w\w\w\w\w\w\w\w\W\w\w\w"	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

6. Matching Start & End

^ - The ^ symbol matches the position at the start of a string.

$ - The $ symbol matches the position at the end of a string.

Non-word characters include characters other than alphanumeric characters (a-z, A-Z and 0-9) and underscore ( _ ).

Regex Pattern - ^123

Test String - 123456

Regex_Pattern = r"^\d\w\w\w\w.$"	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

Character Class

1. Matching Specific Characters

[] - The character class [] matches only one out of several characters placed inside the square brackets.

Regex Pattern - [aeiou] is a vowel

Test String - o is a vowel | e is a vowel

Regex_Pattern = r'^[123][120][xs0][30Aa][xsu][.,]$'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

2. Excluding Specific Characters

[^] - The negated character class [^] matches any character that is not in the square brackets.

Regex Pattern - [^aeiou] is not a vowel

Test String - k is a vowel | p is a vowel

Regex_Pattern = r'^[\D][^aeiou][^bcDF][\S][^AEIOU][^.,]$'  # OR r'^[^\d][^aeiou][^bcDF][^\s][^AEIOU][^.,]$'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

3. Matching Character Ranges

A hyphen (-) inside a character class specifies a range of characters where the left and right operands are the respective lower and upper bounds of the range. For example:

• [a-z] is the same as [abcde...wxyz].
• [A-Z] is the same as [ABCDE...WXYZ].
• [0-9] is the same as [0123456789]. In addition, if you use a caret (^) as the first character inside a character class, it will match anything that is not in that range. For example, matches any character that is not a digit in the inclusive range from to . It's important to note that, when used outside of (immediately preceding) a character or character class, the caret matches the first character in the string against that character or set of characters.

Regex Pattern - [x-z][4-8][A-K]

Test String - x5F

Regex_Pattern = r'^[a-z][1-9][^a-z][^A-Z][A-Z]'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

Repetitions

1. Matching {x} Repetitions

{x} - The tool {x} will match exactly repetitions of character/character class/groups.

Regex Pattern - \w{4}

Test String - H_ck

Regex_Pattern = r'^[a-zA-Z02468]{40}[13579\s]{5}$'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

2. Matching {x, y} Repetitions

{x,y} - The {x,y} tool will match between and (both inclusive) repetitions of character/character class/group.

Regex Pattern - \w{1,4}\d{4,}

Test String - Hk132156545654654654 | Hack1021

Regex_Pattern = r'^\d{1,2}[a-zA-Z]{3,}\.{0,3}$'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

3. Matching Zero Or More Repetitions

• • The * tool will match zero or more repetitions of character/character class/group.

Regex Pattern - Ab*s

Test String - As | Abbbbbs

Regex_Pattern = r'^\d{2,}[a-z]*[A-Z]*$'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

4. Matching One Or More Repetitions

• • The + tool will match one or more repetitions of character/character class/group.

Regex Pattern - Ab+s

Test String - As | Abbbbbs

Regex_Pattern = r'^\d+[A-Z]+[a-z]+$'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())

5. Matching Ending Items

$ - The $ boundary matcher matches an occurrence of a character/character class/group at the end of a line.

Regex Pattern - \w*s$

Test String - Challenges | Hints

Regex_Pattern = r'^[a-zA-Z]*[sS]$'	# Do not delete 'r'.

import re
print(str(bool(re.search(Regex_Pattern, input()))).lower())