Python String split() and join() Methods

Using splitlines()

The splitlines() method is used to split a string at line breaks (\n). It is useful for processing multi-line strings.

Syntax

string.splitlines(keepends)

• keepends: If set to True, it keeps newline characters in the output.

Example: Splitting a Multi-line String

multiline_text = "Hello\nWelcome to Python\nHave a great day!"
lines = multiline_text.splitlines()
print(lines)

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Output:

['Hello', 'Welcome to Python', 'Have a great day!']

The function breaks the string at newline characters and returns a list.

Join the List of Strings into a String

Joining a list means combining multiple elements into a single string with a specified separator.

Using join() Method

The join() method is the most efficient way to join elements of a list into a string.

Syntax

separator.join(iterable)

• separator: The string that separates the elements in the resulting string.
   
• iterable: A list, tuple, or other iterable containing strings.

Example 1: Joining a List into a String

words = ['Python', 'is', 'awesome']
sentence = " ".join(words)
print(sentence)

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Output:

'Python is awesome'

Each word in the list is joined using a space as a separator.

Example 2: Joining with a Custom Separator

fruits = ['apple', 'banana', 'cherry']
csv_format = ",".join(fruits)
print(csv_format)

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Output:

'apple,banana,cherry'

The list elements are joined using a comma.

Example 3: Joining a List of Numbers (Requires Conversion)

numbers = [1, 2, 3, 4]
numbers_str = "-".join(map(str, numbers))
print(numbers_str)

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Output:

'1-2-3-4'

Since numbers cannot be joined directly, they are converted to strings first.

Using for Loop [Less Efficient]

Although the join() method is preferred, a for loop can also be used to concatenate strings.

Example: Joining Using a for Loop

words = ['Hello', 'world', 'Python']
result = ""
for word in words:
    result += word + " "
print(result.strip())

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Output:

'Hello world Python'

However, this approach is inefficient as it repeatedly creates new string objects, increasing execution time.

Frequently Asked Questions

What is the difference between split() and splitlines()?

split() breaks a string based on a specified delimiter, while splitlines() splits at line breaks (\n). splitlines() is useful for multi-line text processing.

Why is join() preferred over a for loop for concatenation?

join() is optimized for string concatenation as it processes all elements in one step, whereas a for loop creates multiple intermediate strings, making it slower.

Can we split a string using multiple delimiters?

No, split only supports one delimiter at a time. However, you can use the re.split() function from the re module for splitting using multiple delimiters.

Conclusion

In this article, we discussed how to split and join strings in Python using various methods. The split() and splitlines() methods help break strings into lists, while the join() method efficiently combines lists into strings. Understanding these functions is crucial for text processing and data handling in Python.