6 Essential Python Regular Expression Examples

In Python, regular expressions play a vital role in dealing with datasets. These metacharacters are critical in use in regular expressions. Here’re the top examples.

List of metacharacters

. ^ $ * + ? { } [ ] \ | ( )

The meaning of the preceding metacharacters is here:

• ? (matches 0 or 1): the expression a? matches the string a (but not ab)
• * (matches 0 or more): the expression a* matches the string aaa (but not baa)
• + (matches 1 or more): the expression a+ matches aaa (but not baa)
• ^ (beginning of line): the expression ^[a] matches the string abc (but not bc)
• $ (end of line): [c]$ matches the string abc (but not cab)
• . (a single dot): matches any character (except newline)

ON THIS PAGE

1. Python regular expression examples
   1. #1 Matching a specific string pattern:
   2. #2 Matching any character in a set:
   3. #3 Matching one or more occurrences of a character:
   4. #4 Matching zero or more occurrences of a character:
   5. #5 Matching a specific number of occurrences of a character:
   6. #6 Removing meta characters from a string

Python regular expression examples

You’ll find the real examples on python regular expression.

• Matching a specific pattern
• Matching any Char
• Matching one of more occurrence of Char
• Matching zero or more occurrence of Char
• Matching specific number of occurrences

#1 Matching a specific string pattern:

The search() methods searches for a pattern.

import re
pattern = "apple"
text = "I like apples and oranges"
match = re.search(pattern, text)
if match:
    print("Match found!")
else:
    print("Match not found!")

The output

Match found!
** Process exited - Return Code: 0 **
Press Enter to exit terminal

#2 Matching any character in a set:

The findall() method will find any matching character.

import re
pattern = "[aeiou]"
text = "Hello, how are you?"
matches = re.findall(pattern, text)
print(matches)

The output

['e', 'o', 'o', 'a', 'e', 'o', 'u']
** Process exited - Return Code: 0 **
Press Enter to exit terminal

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#3 Matching one or more occurrences of a character:

import re
pattern = "o+"
text = "Hello, how are you?"
matches = re.findall(pattern, text)
print(matches)

The output

['o', 'o', 'o']
** Process exited - Return Code: 0 **
Press Enter to exit terminal

#4 Matching zero or more occurrences of a character:

import re
pattern = "o*"
text = "Hello, how are you?"
matches = re.findall(pattern, text)
print(matches)

The output

['', '', '', '', 'o', '', '', '', 'o', '', '', '', '', '', '', '', 'o', '', '', '']
** Process exited - Return Code: 0 **
Press Enter to exit terminal

#5 Matching a specific number of occurrences of a character:

import re
pattern = "o{2}"
text = "Hello, how are you?"
matches = re.findall(pattern, text)
print(matches)

The output

[]
** Process exited - Return Code: 0 **
Press Enter to exit terminal

#6 Removing meta characters from a string

The sub() method removes meta characters from the string.

import re
text1 = "meta characters ? and / and + and ."
text2 = re.sub("[/\.*?=+]+","",text1)
print('text1:',text1)
print('text2:',text2)

The output

text1: meta characters ? and / and + and .
text2: meta characters  and  and  and 
** Process exited - Return Code: 0 **
Press Enter to exit terminal

Summary

• These are a few examples that you can do with regular expressions in Python.
• Regular expressions are a powerful tool for working with text, searching for specific patterns, validating input, etc.

References

• Mastering Python regular expressions
• Python regular expressions a pocket reference book
• The Python Examples from Google Tutorial
• Python Regular Expressions-NTU university Singapore