Using split() is a simple and efficient method for breaking down large strings into more manageable parts.

This can be a useful method if we’re tasked with working on text files, as we’ll see later on.

Definition and Syntax of the Split Function

The split() method separates a string into individual words using a delimiter, also referred to as the separator. Python uses whitespace as the default separator, but you are free to provide an alternative.

The separator can be anything, but it’s generally a character used to separate the words in a string. For example, a comma is often used to break up a list.

# the following string uses a comma as the separator.
groceries = “Bread,Milk,Eggs,Bananas,Coffee”

The split() function will return a list of strings. By default there is no limit to how long the returned list can be. But you can change this with the maxsplit setting.

Syntax:

my_string.split(separator,maxsplit)

separator: This is the delimiter Python will use to split the string. Whitespace is used as the separator if one is not provided.

maxsplit: This setting is used to determine how many times the string should be split. This list has no limit by default.

Why Use the split() Function in Python?

There are plenty of good reasons to use the split() function. Whether you’re working with a comma separated value (CSV) file, or simply trying to break down a large string into smaller pieces, split() offers an efficient means of splitting strings in Python.

The split() function will break a string into list of words. These are given back to us in the form of a Python string array.

Here’s a step-by-step guide to using split():

1. Create a string.
2. Use the Python split() function
3. Print the result

gandalf = "You shall not pass."
gandalf.split() # The string will be split based on whitespace.

Here’s what it looks like when we split the string.

['You', 'shall', 'not', 'pass.']

Use the split() function with python string concatenation to quickly join and split strings. The split() function is also great for quickly parsing comma separated value (CSV) files.

Examples of the Python Split Function

When we use the split() function to split a string, Python returns a new string array. This array holds the split string.

For example. If we have a string that looks like this:

frosty_string = "Some say the world will end in fire."

We can see that the words of the string are separated by whitespace. Running split() with this string would return a new array containing the words of the opening line of a famous poem by Robert Frost.

Example 1: Using Python split() With a Basic String

# this line is from Fire and Ice by Robert Frost
frosty_string = "Some say the world will end in fire."
words = frosty_string.split()
print(words)

Output

['Some', 'say', 'the', 'world', 'will', 'end', 'in', 'fire.']

It’s also possible to use split() to break a list into a predefined number of parts. As we saw in its definition, the split() function takes an optional second argument. By setting maxpslit, we can tell Python to break the list into two pieces.

Example 2: Breaking a List Into Two Parts Using Python Split

fruit = "Apples Oranges"
# setting maxsplit to 1 will return a list with 2 parts
two_max = fruit.split(' ', 1)
print(two_max)

Output

['Apples', 'Oranges']

Using Commas to Split String Data

We’ve seen a basic use of the split() function. By default, split() uses whitespace to split strings. While whitespace works for some data, other characters often make more sense. It’s common to use a comma to separate values in a string.

Using commas, we can easily split a large amount of string data quickly. In the following example, a string containing all the instruments in a generic rock band is split into a new list.

Example 3: Using a Comma as the Separator

# use a comma as the separator
band = "Guitar,Piano,Drums,Trumpet,Bass Guitar,Vocals"
instruments = band.split(',')
print(instruments)

Output

['Guitar', 'Piano', 'Drums', 'Trumpet', 'Bass Guitar', 'Vocals']

Using a comma as the separator makes it easy to convert a string into a list. Converting strings into lists, and vice versa, can be a convenient method of storing and reading data.

Reading Text Files With Split() Function

I’ve created a text file on my computer called chess.txt. This file is located in the same folder as my Python file.

This text file contains a single line listing the pieces used in a game of chess. Notice that a comma is used to separate the names of the pieces.

King,Queen,Rook,Knight,Bishop,Pawn

By utilizing split(), we can easily separate the game pieces. We’ll use Python’s open() method to read the file and extract the line of text before splitting the string.

Example 4: Using split() to separate words in a text file

file = open("chess.txt")

pieces = file.read().split(',')

print(pieces)

Output

['King', 'Queen', 'Rook', 'Knight', 'Bishop', 'Pawn\n']

Using Strip() With the Split() Function

Looking back at the last example, you might notice something odd about our list. We’ve picked up some stray characters somewhere. Where did that \n come from?

This is the new line character. It tells Python that we’ve come to the end of the line in a text file.
 
We can make use of Python’s strip() method to remove the new line character from the end of our list. Using this method will ensure that we don’t pick up any pesky hidden characters from the file, such as the \n character.

file = open("chess.txt")
pieces = file.read().strip().split(',')
print(pieces)
file.close()

Output

['King', 'Queen', 'Rook', 'Knight', 'Bishop', 'Pawn']

Splitting Multiple Lines of Text

The above example was relatively basic. After all, we only had one line of text to deal with. But what if we have rows of data separated by commas? Let’s take a look at what reading a simple database might look like.

We’ll write a program for a teacher who needs to calculate the average grades for each student in his/her class.

Our client needs to keep track of his/her student’s homework. Specifically, he/she would like a way to read the data stored in a text file. The file, called grades.txt, contains the grades of the teacher’s students.

Our teachers_pet.py program will read the information from a file and build a string containing the grade data. 

Once we have the string of grades, we can use the split() function to split the grades and store them in a list. After that, we’ll need to convert the strings to numbers using the float() method.

While this is admittedly a convoluted process, the example demonstrates the various ways one can work with numbers and strings in Python.

grades.txt
Noah, 81, 94, 100, 65
Elijah, 80, 84, 72, 79
Lucas, 95, 80, 89, 89
Emma, 95, 80, 80, 77
Ava, 90, 84, 85, 80
Amelia 100, 100, 95, 0

Example 5: The Teachers Pet Project

# teachers_pet.py
file = open("grades.txt", 'r')

grade_data = []

while(True):
    line = file.readline()
    if not line:
        break

    grade_data.append(line.split(','))

print(grade_data)
file.close()

# this function will loop through the student's grades
def calculate_averages(grades_data):
    for grades in grade_data:
        total = 0
        # the student's name occupies the first spot
        for i in range(1,len(grades)):
            total += float(grades[i].strip()))
        avg = total/float(len(grades)-1)
        print("{} has an average of {}.".format(grades[0],avg))

calculate_averages(grade_data)

Output

Noah has an average of 85.0
Elijah has an average of 78.75
Lucas has an average of 88.25
Emma has an average of 83.0
Ava has an average of 84.75
Amelia has an average of 73.75

Our program has two parts. In the first part, we read the data from the file with the open() method. Line by line, the grades of each student are added to a list called grades_data.

We do this by taking advantage of float() to convert the string to a number. We’ll also use strip() to remove any unnecessary characters, such as the \n character.

Keep in mind that the first element in the list of grades is the student’s name.

We also need a function to calculate and print the grade averages. We do this in calculage_averages(). This handy function will look through the grade data and find each student’s grade point average.

Lessons for Further Study

Python comes with many built-in functions that can improve your code. The split() function is one such tool that can be used to break up difficult string problems.

Using a separator to divide the string allows you to convert string data into a list of strings, which is easier to manage. The split() function is also a quick way break up text data read from a file.

Learn more about Python and how to improve your programming skills by visiting the following tutorials. 

• Learn how to use comments to improve your Python code
• How to use Python concatenation to join strings

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Introducing The split() Method in Python

The fastest way to split text in Python is with the split() method. This is a built-in method that is useful for separating a string into its individual parts.

The split() method, when invoked on a string, takes a delimiter as its input argument. After execution, it returns a list of the substrings in the string. By default, Python uses whitespace as a delimiter to split the string, but you can provide a delimiter and specify what character(s) to use instead.

For example, a comma(,) is often used to separate string data. This is the case with Comma Separated Value (CSV) files. Whatever you choose as the separator, Python will use to split the string.

Splitting A Text File With The split() Method in Python

In our first example, we have a text file of employee data, including the names of employees, their phone numbers, and occupations. We’ll need to write a Python program that can read this randomly generated information and split the data into lists. To start with, first, save the following text into a file named employee_data.txt.

Lana Anderson 485-3094-88 Electrician
Elian Johnston 751-5845-87 Interior Designer
Henry Johnston 777-6561-52 Astronomer
Dale Johnston 248-1843-09 Journalist
Luke Owens 341-7471-63 Teacher
Amy Perry 494-3532-17 Electrician
Chloe Baker 588-7165-01 Interior Designer

We will first open the above file in read mode using Python with open statement. Here, the open() method takes the file name as its first input argument and the Python literal “r” as its second input argument. After execution, the open() method returns a file pointer that we will assign to the data_file variable. After this, we can iterate through the file’s contents using a for loop. Once the data is read, we can use the split() method to separate the text into words.

Example 1: Splitting employee data with Python

The following code shows how to split a text file using the split() method in Python. In the example, we have used the “employee_data.txt” file defined above.

with open("employee_data.txt",'r') as data_file:
    for line in data_file:
        data = line.split()
        print(data)

Output

['Lana', 'Anderson', '485-3094-88', 'Electrician']
['Elian', 'Johnston', '751-5845-87', 'Interior', 'Designer']
['Henry', 'Johnston', '777-6561-52', 'Astronomer']
['Dale', 'Johnston', '248-1843-09', 'Journalist']
['Luke', 'Owens', '341-7471-63', 'Teacher']
['Amy', 'Perry', '494-3532-17', 'Electrician']
['Chloe', 'Baker', '588-7165-01', 'Interior', 'Designer']

In the above example, you can observe that the output contains a list of words for each line in the text file. In this case, the text is split at whitespaces, which is the default behavior of the split() method.

Splitting Strings With a Comma in Python

We can also split a text file at commas using the split() method in Python. For this, we can provide the comma character as an optional separator to the split() method to specify which character to split the string with.

To discuss how to split a text file at comma using the split() method in Python, let us first create a text file containing commas as shown below.

Janet,100,50,69
Thomas,99,76,100
Kate,102,78,65

You can save the data in the above snippet as grades.txt.

Example 2: Splitting grades with a comma

To split a text file with a comma in Python, we will first open the file. Then, we will read the file line by line using a for loop. We will first remove any extra spaces or newline characters from each line using the strip() method. The strip() method, when invoked on a string, removes any spaces or newline characters from the start and end of a string.

Next, we will invoke the split() method on the string returned by the strip() method and pass the comma character “,” as its input argument. After execution, the split() method returns a list having sub-strings of the original lines in the text file separated at commas. You can observe this in the following example.

with open("grades.txt",'r') as file:
    for line in file:
        grade_data = line.strip().split(',')
        print(grade_data)

The output of the above code looks as follows.

['Janet', '100', '50', '69']
['Thomas', '99', '76', '100']
['Kate', '102', '78', '65']

Splitting a Text File With splitlines() Method in Python

The splitlines() method is used to get a list of the lines in a text file. For the next examples, we’ll pretend we run a website that’s dedicated to a theatre company. We’re reading script data from text files and pushing it to the company’s website. To proceed ahead, you can save the following lines in a text file “juliet.txt”.

O Romeo, Romeo, wherefore art thou Romeo?
Deny thy father and refuse thy name.
Or if thou wilt not, be but sworn my love
And I'll no longer be a Capulet.

We can read the text file and split it at the newline characters with the splitlines() method to obtain a list of lines. Afterward, You can use a for loop to print the contents of the list as shown below.

Example 3: Using splitlines() to read a text file

In the following example, we will read the juliet.txt file into a variable named “script”. Then, we will use the read() method to read the contents of the file. After that, we will use the splitlines() method to split the text file into a list of lines. We will store the list in the variable “speech”. Finally, we will print the list contents using a for loop as shown below.

with open("juliet.txt",'r') as script:
    speech = script.read().splitlines()
print("The list is:")
print(speech)
for line in speech:
    print(line)

When we execute the above Python code, the output looks as follows.

Using a Generator to Split a Text File in Python

In Python, a generator is a special routine that we can use to create an iterable object. A generator in Python is similar to a function that returns an iterable object, but it does so one element at a time.

Generators use the yield keyword. When Python encounters a yield statement, it stores the state of the function until later, when the generator is called again.

In the next example, we’ll use a generator to read the beginning of Romeo’s famous speech from Shakespeare’s Romeo and Juliet. Using the yield keyword ensures that the state of our while loop is saved during each iteration. This can be useful when working with large files. To proceed ahead, let us create a file named romeo.txt with the following text.

But soft, what light through yonder window breaks?
It is the east, and Juliet is the sun.
Arise, fair sun, and kill the envious moon,
Who is already sick and pale with grief
That thou, her maid, art far more fair than she.

Example 4: Splitting a text file with a generator

We can split the above text file using a generator in Python as shown in the following example.

In the following code, we first create a generator named generator_read() that takes a file name as its input. It opens the file in read mode and reads the file contents using a while loop and the readline() method. Then, it gives each line as output using the yield statement.

When executed, it returns the contents of the line by line in a generator named file_data. We can iterate over this generator to access the file contents line by line. Finally, we will use the split() method to split each line of the text in Python using a generator as shown below.

def generator_read(file_name):
    file = open(file_name,'r')
    while True:
        line = file.readline()
        if not line:
            file.close()
            break
        yield line

file_data = generator_read("romeo.txt")
print("The generator is:")
print(file_data)
print("The file contents are:")
for line in file_data:
    print(line.split())

The output of the above code looks as follows.

Reading File Data with List Comprehension

Python list comprehension provides an elegant solution for working with lists. We can take advantage of shorter syntax to write our code with list comprehension instead of the for loop to read a file. In addition, list comprehension statements are usually easier to read.

In our previous examples, we’ve had to use a for loop to read the text files. We can exchange our for loop for a single line of code using list comprehension.

For this, we will first read open a file using the open() method. Then, we will use list comprehension to create a list of lines in the file.

Once we get the data via list comprehension, we will use the split() method to split the lines and add them to a new list as shown below.

with open("romeo.txt",'r') as file:
    lines = [line.strip() for line in file]
print("The list is:")
print(lines)
print("The data after splitting is:")
for line in lines:
    print(line.split())

The output of the above code looks as follows.

The list is:
['But soft, what light through yonder window breaks?', 'It is the east, and Juliet is the sun.', 'Arise, fair sun, and kill the envious moon,', 'Who is already sick and pale with grief', 'That thou, her maid, art far more fair than she.']
The data after splitting is:
['But', 'soft,', 'what', 'light', 'through', 'yonder', 'window', 'breaks?']
['It', 'is', 'the', 'east,', 'and', 'Juliet', 'is', 'the', 'sun.']
['Arise,', 'fair', 'sun,', 'and', 'kill', 'the', 'envious', 'moon,']
['Who', 'is', 'already', 'sick', 'and', 'pale', 'with', 'grief']
['That', 'thou,', 'her', 'maid,', 'art', 'far', 'more', 'fair', 'than', 'she.']

Split a Text File into Multiple Smaller Files in Python

What if we have a large file that we’d like to split into smaller files? We split a large file in Python using for loops and slicing.

With list slicing, we tell Python we want to work with a specific range of elements from a given list. This is done by providing a start point and end point for the slice.

In Python, a list can be sliced using the indexing operator. In the following example, we’ll use list slicing to split a text file into multiple smaller files.

Split a File with List Slicing in Python

To split a text file into multiple files in python, we can use list slicing. For this, we will first open the file in read mode. Then, we will obtain a list of lines in the text file using the readlines() method. Next, the top half of the file is written to a new file called romeo_A.txt. We’ll use list slicing within this for loop to write the first half of the original file to a new file. Using a second for loop, we’ll write the rest of the text to another file. In order to perform the slice, we will also use the len() method to find the total number of lines in the original file.

You can observe this in the following example.

with open("romeo.txt",'r') as file:
    lines = file.readlines()

with open("romeo_A.txt",'w') as file:
    for line in lines[:int(len(lines)/2)]:
        file.write(line)

with open("romeo_B.txt",'w') as file:
    for line in lines[int(len(lines)/2):]:
        file.write(line)

Running this program in the same directory as romeo.txt will create the following text files.

romeo_A.txt
But soft, what light through yonder window breaks?
It is the east, and Juliet is the sun.

romeo_B.txt
Arise, fair sun, and kill the envious moon,
Who is already sick and pale with grief
That thou, her maid, art far more fair than she.

Conclusion

In this article, we discussed how to use the split() method to split a text file in Python. Additionally, our examples have shown how the split() method is used in tandem with Python generators and list comprehension to read large files more elegantly. Taking advantage of Python’s many built-in methods, such as split() and readlines(), allows us to process text files more quickly. Using these tools will save us time and effort.

If you’re serious about mastering Python, it’s a good idea to invest some time in learning how to use these methods to prepare your own solutions. If you’d like to learn more about programming with Python, you can read this article on tuple comprehension in Python. You might also like this article on unpacking in Python.

I hope you enjoyed reading this article. Stay tuned for more informative articles.

Happy learning!

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Definition

The split() method splits a string into a list using a user specified separator. When a separator isn’t defined, whitespace(” “) is used.

Why use the Split() Function?

At some point, you may need to break a large string down into smaller chunks, or strings. This is the opposite of concatenation which merges or combines strings into one.

To do this, you use the python split function. What it does is split or breakup a string and add the data to a string array using a defined separator.

If no separator is defined when you call upon the function, whitespace will be used by default. In simpler terms, the separator is a defined character that will be placed between each variable.

Examples of the Python Split Function In Action

Let’s take a look at some examples.

x = ‘blue,red,green’
x.split(“,”)
 
[‘blue’, ‘red’, ‘green’]
>>>
 
>>> a,b,c = x.split(“,”)
 
>>> a
‘blue’
 
>>> b 
‘red’
 
>>> c
‘green’

As you can see from this code, the function splits our original string which includes three colors and then stores each variable in a separate string. This leaves us with three strings of “a”, “b”, and “c”. Then, when you ask the interpreter to spit out the variables stored in these strings, you get the appropriate color.

Pretty neat, no? It’s also extremely useful when you’re working extensively with strings and variables.

Let’s look at another example.

>>> words = “This is random text we’re going to split apart”
 
>>> words2 = words.split(“ “)
 
>>> words2

[‘This’, ‘is’, ‘random’, ‘text’, ‘we’re’, ‘going’, ‘to’, ‘split’, ‘apart’]

What we did here is split the larger string and store the variables as a list under the “words2” string.

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