![]() ![]() AnchorsĪnchors specify the position of the pattern in the text. We can use character sets to match any set of characters that we’re interested in. The text contains a mixture of alphabets, digits, and special characters.Īs we can see, the regular expressions for character sets correctly match the patterns we defined and return the expected output. We then define a sample text to test the regular expressions. The first pattern matches any digit from 0 to 9 with, the second pattern matches any lowercase alphabet from a to z with, the third pattern matches any uppercase alphabet from A to Z with, and the fourth pattern matches any alphabet (uppercase or lowercase) with. In this example, we define four regular expressions using the re.compile() function. Here’s the Python code to implement regular expressions for character sets: import re # Matches any digit from 0 to 9 pattern1 = re.compile(r'') # Matches any lowercase alphabet from a to z pattern2 = re.compile(r'') # Matches any uppercase alphabet from A to Z pattern3 = re.compile(r'') # Matches any alphabet (uppercase or lowercase) pattern4 = re.compile(r'') # Sample text to test the regular expressions text = 'The quick brown fox jumps over the lazy dog 123 times!' # Test pattern1 print(pattern1.findall(text)) # Output: # Test pattern2 print(pattern2.findall(text)) # Output: # Test pattern3 print(pattern3.findall(text)) # Output: # Test pattern4 print(pattern4.findall(text)) # Output: ![]() ![]() : Matches any alphabet (uppercase or lowercase).: Matches any uppercase alphabet from A to Z.: Matches any lowercase alphabet from a to z.Here are some commonly used character classes: Character ClassesĬharacter classes define a set of characters that match a single character in the text. We can use these metacharacters to create powerful regular expressions to match complex patterns in text. We use the findall() method to search for all occurrences of the pattern in the sample text, and print the output to the console.Īs we can see, the regular expressions using these metacharacters correctly match the patterns we defined and return the expected output. The text contains a mixture of characters, including spaces, alphabets, and words. And the sixth pattern denotes alternation, which matches either the preceding or the following pattern, with cat|dog. The fifth pattern denotes a character class, which matches any single character within the brackets, with. The fourth pattern matches zero or one occurrence of the preceding character or group with ab?. The second pattern matches zero or more occurrences of the preceding character or group with ab*, and the third pattern matches one or more occurrences of the preceding character or group with ab+. The first pattern matches any single character except a newline with. In this example, we define six regular expressions using the re.compile() function. Here’s the Python code to implement regular expressions using these metacharacters: import re # Matches any single character except a newline pattern1 = re.compile(r'.') # Matches zero or more occurrences of the preceding character or group pattern2 = re.compile(r'ab*') # Matches one or more occurrences of the preceding character or group pattern3 = re.compile(r'ab+') # Matches zero or one occurrence of the preceding character or group pattern4 = re.compile(r'ab?') # Denotes a character class, which matches any single character within the brackets pattern5 = re.compile(r'') # Denotes alternation, which matches either the preceding or the following pattern pattern6 = re.compile(r'cat|dog') # Sample text to test the regular expressions text = 'The quick brown fox jumps over the lazy dog' # Test pattern1 print(pattern1.findall(text)) # Output: # Test pattern2 print(pattern2.findall('ab abb aabb')) # Output: # Test pattern3 print(pattern3.findall('ab abb aabb')) # Output: # Test pattern4 print(pattern4.findall('ab abb aabb')) # Output: # Test pattern5 print(pattern5.findall('The quick brown fox jumps over the lazy dog')) # Output: # Test pattern6 print(pattern6.findall('I have a cat and a dog as pets')) # Output: A vertical bar (|) denotes alternation, which matches either the preceding or the following pattern.Square brackets () denote a character class, which matches any single character within the brackets.A question mark (?) matches zero or one occurrence of the preceding character or group.A plus sign (+) matches one or more occurrences of the preceding character or group.An asterisk (*) matches zero or more occurrences of the preceding character or group.A period (.) matches any single character except a newline.Here are some of the basic regex syntax rules: Regex syntax consists of a combination of characters and metacharacters that define the pattern to match. ![]()
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