Python Split String – How to Split a String into a List or Array in Python

Strings are one of the fundamental data types in Python, used to represent text. In many cases, you‘ll need to break apart string data into smaller pieces for processing and analysis. Python provides several built-in methods and modules to make splitting strings into lists or arrays straightforward.

In this in-depth guide, we‘ll explore the various ways to split strings in Python. Whether you‘re a beginner or a seasoned Python developer, you‘ll gain a thorough understanding of how to effectively split strings for a variety of use cases. Let‘s dive in!

The split() Method

The split() method is the most common and simplest way to split a string into a list of substrings in Python. By default, it splits on whitespace (spaces, tabs, newlines). Here‘s a basic example:

text = "Hello world how are you doing today?"
words = text.split()
print(words)

Output:

[‘Hello‘, ‘world‘, ‘how‘, ‘are‘, ‘you‘, ‘doing‘, ‘today?‘] 

The split() method returns a list containing the substrings. If the string is empty or only contains whitespace, it returns an empty list.

You can also specify a delimiter to split on something other than whitespace:

csv_row = "john,doe,42,new york"  
data = csv_row.split(",")
print(data)

Output:

[‘john‘, ‘doe‘, ‘42‘, ‘new york‘]

This is commonly used for parsing structured text data like CSV files or log entries.

By default, split() splits on every occurrence of the delimiter. If you only want to split a certain number of times, pass the maxsplit argument:

text = "one||two||three||four"
print(text.split("||", maxsplit=2)) 

Output:

[‘one‘, ‘two‘, ‘three||four‘]

The string is only split on the first 2 occurrences of "||", leaving the rest intact. Using maxsplit can be useful for splitting data like names, where you want to separate the first and last name but leave any middle names together.

Splitting Multiline Strings with splitlines()

For multiline strings, the splitlines() method is the natural choice. It splits on any universal newline character (‘\n‘, ‘\r‘, ‘\r\n‘) and returns a list of lines without the trailing newlines:

poem = """
Roses are red
Violets are blue
Python is awesome 
And so are you!
"""

lines = poem.splitlines()
print(lines)

Output:

[‘‘, ‘Roses are red‘, ‘Violets are blue‘, ‘Python is awesome‘, ‘And so are you!‘]

Notice that if the string starts with a newline, it results in an empty string as the first list element.

An alternative is to use split() with ‘\n‘ as the delimiter:

lines = poem.split(‘\n‘)

The key difference is that splitlines() handles all newline types (‘\n‘, ‘\r‘, ‘\r\n‘) while split(‘\n‘) only handles ‘\n‘. splitlines() is more cross-platform friendly.

Splitting Strings with Regular Expressions

For more advanced string splitting, you can use regular expressions via the re module. This allows you to split on complex patterns beyond a single character delimiter.

For example, to split on whitespace or any punctuation character:

import re

text = "Hey, how are you? I‘m doing fine thank you."
parts = re.split(r‘[\s.,?!]+‘, text) 
print(parts)

Output:

[‘Hey‘, ‘how‘, ‘are‘, ‘you‘, "I‘m", ‘doing‘, ‘fine‘, ‘thank‘, ‘you‘, ‘‘]

The regular expression [\s.,?!]+ matches any whitespace character (\s) or the punctuation .,?! one or more times (+).

You can also use capture groups in the regex to include the delimiter in the resulting list:

import re

text = "apple-pear-grape-banana"  
parts = re.split(r‘(-)‘, text)
print(parts)

Output:

[‘apple‘, ‘-‘, ‘pear‘, ‘-‘, ‘grape‘, ‘-‘, ‘banana‘]

The (-) captures the – delimiter itself to be included as a separate element.

Regular expressions are incredibly powerful for splitting strings in complex ways. However, for simpler cases, split() and splitlines() are usually more readable and straightforward.

Other Ways to Split Strings

Python provides a few other methods for splitting strings in special cases:

partition() splits a string into three parts based on the first occurrence of a separator:

name = "John Smith"
first, separator, last = name.partition(‘ ‘)
print(first)    # "John"
print(separator)  # " " 
print(last)     # "Smith"

This can be handy when you need to split into exactly two or three logical parts and preserve the separator.

You can also use slice notation to manually split a string:

text = "abcdefg"
print(text[0:3])  # "abc"
print(text[3:])   # "defg"  

However, this is inflexible compared to the other methods since you need to know the exact indices to slice on.

Choosing the Right Splitting Approach

With multiple ways to split strings in Python, which one should you choose? Here are some general recommendations:

• For simple splitting on whitespace or a single character delimiter, use split(). It‘s by far the most common method.

• For splitting multiline strings, splitlines() is the clear choice. It handles all newline types and is cross-platform friendly.

• If you need to split on a more complex pattern like punctuation, digits, or multiple delimiters, use re.split(). Regular expressions offer the most power and flexibility.

• In the rare case you need to split into three parts and preserve the separator, use partition().

In the end, the choice depends on your specific use case. Most of the time, split() is all you need. But it‘s important to know the alternatives for when you encounter more complex string splitting problems.

Conclusion

In this article, we‘ve covered the essentials of splitting strings in Python:

• Using split() to split on whitespace or a specific delimiter
• Handling multiline strings with splitlines()
• Splitting with regular expressions via re.split()
• Alternatives like partition() and slice notation

Splitting strings is a core skill for any Python programmer. Whether you‘re parsing user input, processing text data, or manipulating strings, you‘ll encounter string splitting on a daily basis. Mastering the various methods and their use cases will make you a more proficient and efficient Python developer.

Remember, strings are immutable in Python. Splitting them always returns a new list rather than modifying the original string. Keep this in mind as you process and manipulate string data in your programs.

Now you‘re equipped with a comprehensive understanding of splitting strings in Python. Go forth and split some strings!