When working with Python, it is common to encounter situations where you need to apply a specific format to each line of a message that contains new lines. One such scenario is when you are dealing with logging and want to format the log message in a specific way. In this article, we will explore three different ways to solve this problem using Python.

Option 1: Using a Loop

One way to solve this problem is by using a loop to iterate over each line of the message and apply the desired format. Here’s an example:

message = "This is anmultiline messagenwith new lines"

formatted_message = ""
for line in message.split("n"):
    formatted_message += f"[LOG] {line}n"

print(formatted_message)

In this code snippet, we split the message into individual lines using the `split()` method and iterate over each line using a loop. Inside the loop, we append the desired format to each line and add a new line character at the end. Finally, we print the formatted message.

Option 2: Using List Comprehension

Another way to solve this problem is by using list comprehension. List comprehension provides a concise way to apply a transformation to each element of a list. Here’s an example:

message = "This is anmultiline messagenwith new lines"

formatted_message = "n".join([f"[LOG] {line}" for line in message.split("n")])

print(formatted_message)

In this code snippet, we use list comprehension to iterate over each line of the message, apply the desired format, and create a new list. We then join the elements of the list using the `join()` method, specifying the newline character as the separator. Finally, we print the formatted message.

Option 3: Using Regular Expressions

A third way to solve this problem is by using regular expressions. Regular expressions provide a powerful and flexible way to search, match, and manipulate strings. Here’s an example:

import re

message = "This is anmultiline messagenwith new lines"

formatted_message = re.sub(r"(?m)^", "[LOG] ", message)

print(formatted_message)

In this code snippet, we use the `re.sub()` function from the `re` module to substitute the start of each line (`^`) with the desired format (`[LOG]`). The `(?m)` flag enables multiline mode, allowing the `^` anchor to match the start of each line. Finally, we print the formatted message.

After exploring these three options, it is clear that the second option, using list comprehension, is the most concise and readable solution. It leverages the power of list comprehension to apply the desired format to each line and join them back together using the newline character as the separator. This approach is not only efficient but also easy to understand and maintain.