Python .replace() regex

In Python, the .replace() method is used to replace fixed substrings, but it doesn't support regular expressions (regex). If you're looking to do pattern-based replacements using regex, you should use the re.sub() method from the re module instead.

Here’s the difference and how to use it effectively:

.replace() method (no regex support)

• Replaces exact matches of a substring.
  
• Syntax: string.replace(old, new)
  

Example:

text = "Hello 123"

print(text.replace("123", "456"))  # Output: Hello 456

re.sub() method (regex support)

• Allows pattern matching and replacement using regex.
  
• Syntax: re.sub(pattern, replacement, string)
  

Example:

import re

text = "Order123, Code456"

new_text = re.sub(r'd+', '###', text)

print(new_text)  # Output: Order###, Code###

Key Points:

• Use .replace() for simple, direct substitutions.
  
• Use re.sub() for advanced pattern matching and dynamic replacements.
  
• re.sub() also supports callback functions for complex replacements.
  

So, if you need regex, stick with re.sub(). Trying to use .replace() with regex won't work and can lead to confusion.