Python RegEx, short for Regular Expressions, is a powerful tool used for pattern matching and text manipulation. It is a sequence of characters that define a search pattern. Python RegEx is used to search, replace, and extract information from strings based on patterns.
Python RegEx is a module that is included in the Python standard library. It provides a set of functions that can be used to work with regular expressions. The module is called "re" and it can be imported into your Python code using the following statement:
<per>import re</per>Once the "re" module is imported, you can start using Python RegEx to search for patterns in strings.
Python RegEx uses a specific syntax to define patterns. The syntax is made up of a combination of characters and special symbols that represent different types of characters and patterns. Here are some of the most commonly used symbols:
. - Matches any character except a newline character.^ - Matches the start of a string.$ - Matches the end of a string.* - Matches zero or more occurrences of the preceding character.+ - Matches one or more occurrences of the preceding character.? - Matches zero or one occurrence of the preceding character.{} - Matches a specific number of occurrences of the preceding character.[] - Matches any one of the characters inside the brackets.| - Matches either the expression before or after the symbol.() - Groups expressions together.The "re" module provides a set of functions that can be used to work with regular expressions. Here are some of the most commonly used functions:
re.search() - Searches the string for a match to the pattern.re.match() - Searches the string only at the beginning for a match to the pattern.re.findall() - Returns a list of all matches in the string.re.sub() - Replaces one or many matches with a string.re.split() - Splits the string at the matches.Here are some examples of how to use Python RegEx:
The following code searches for the pattern "world" in the string "Hello, world!":
<per>import re
string = "Hello, world!"
pattern = "world"
result = re.search(pattern, string)
print(result)</per>The output of this code will be:
<per><re.Match object; span=(7, 12), match='world'></per>This means that the pattern "world" was found in the string at positions 7 to 12.
The following code replaces all occurrences of the pattern "world" with the string "Python" in the string "Hello, world!":
<per>import re
string = "Hello, world!"
pattern = "world"
replacement = "Python"
result = re.sub(pattern, replacement, string)
print(result)</per>The output of this code will be:
<per>Hello, Python!</per>This means that all occurrences of the pattern "world" were replaced with the string "Python" in the original string.
The following code extracts all email addresses from a string:
<per>import re
string = "My email is john@example.com and my friend's email is jane@example.com."
pattern = r"\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b"
result = re.findall(pattern, string)
print(result)</per>The output of this code will be:
<per>['john@example.com', 'jane@example.com']</per>This means that all email addresses were extracted from the original string and returned as a list.
Python RegEx is a powerful tool that can be used for pattern matching and text manipulation. It provides a set of functions that can be used to work with regular expressions. By using Python RegEx, you can search, replace, and extract information from strings based on patterns.