Introduction to the split() function in Python

Split function in Python is a string manipulation tool that helps you to easily handle a big string into smaller strings by splitting it. This function works as opposed to the concatenation of strings, which combines various strings into one. It assesses a string and isolates when it observes a separator that has already been specified. 

If the split function doesn’t find any predefined separator from the Python split list, it, by default, utilises white space. Moreover, the function returns a list comprising words post separating a line or string using a delimiter string like the comma (,) character.

Wondering how to use split function in Python? Keep reading to understand all about this function for improved implementation!

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Basic Syntax and Parameters

Here’s the syntax of the Python split function:

string.split(separator,max)

Let’s understand the meaning of each of these parameters:

Separator:

The separator tells Python where to split the string. Essentially, it performs as a delimiter and separates strings based on the predefined separator. The string splits at your mentioned separator. This parameter is an option, so if you don’t specify a separator, the split function will leverage white space as the default separator.

It works as a predefined Python split string by character, which is placed between each variable present in the output.

Maxsplit:

You must understand the importance of this parameter if you want to learn how to use split function in Python. It is a number that informs exactly how many times a string is required to be split. It is optional. So, if it is not specified, the default value is -1.

There is no limit on the value of Maxsplit which implies that there is no bound on how many times a string can be split.

After the function breaks the string by the mentioned separator, it returns a Python split list of strings.

Usually, these parameters work on split string Python by character.

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Splitting a String into a List of Substrings

In Python, splitting a string into a list consisting of a delimiter means that the output shows a subdivided list of substrings. Any delimiter can work like a separator in the Python split string function to break into a list of strings.

Here’s an instance of how a string can be split into a list :

str = “Year-Month-Day”
print(str.split(“-”))

Here’s the output:

['Year', 'Month', 'Day']

In the above example of Python split string by character, the str variable is declared with a string containing dash characters (-) in between, used as a separator. This operation divides the string every time it sees a dash. The corresponding output of split string Python by character is a list of substrings.

Specifying the Separator for Splitting

The default separator in Python split string is any whitespace.

Here’s an example demonstrating how to specify the separator for splitting.

subj = 'English,Geography,Maths, GK'
print(subj.split(','))
vegetables = 'potato$onion$cabbage$peas'
print(vegetables.split('$'))

Output

['English', 'Geography', 'Maths', ‘GK’]
['potato', 'onion', 'cabbage', 'peas']

In the first example above, the subj.split(‘,’) function specifies a comma as a separator.

In the second example above, the vegetables.split(‘$’) mentions the $ symbol as a separator. Hence, the split() method splits a string at each separator and incorporates each part of a string into a list.

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Limiting the Number of Splits

You can limit the number of splits by simply specifying the number in the second parameter of the Python split function.

The below example limits the split by mentioning the number in the maxsplit parameter.

subj = 'English,Geography,Maths, GK'
print(subj.split(',', 2))
vegetables = 'potato$tomato$onion$peas'
print(vegetables.split('$', 2))

Output:

['English', 'Geography', 'Maths, GK']
['potato', 'tomato', 'onion$peas']

In the above example, the subj.split(‘,’, 2) defines 2 as maxsplit argument. Hence, it splits the subj string 2 times, and the list object contains four elements. The third element shows the remaining string.

In the vegetables.split(‘$’, 2) function, the string is split up two times. The returned list consists of three elements.

Splitting a String from the End

There is a split method in Python that splits the string from the end of the string. The built-in Python function rsplit() splits the string on the delimiter’s last occurrence.

Here is the syntax of rsplit() function.

rsplit("delimiter", argument)
Example:
rsplit("delimiter",1)

In the above rsplit() function, 1 is passed as the argument. Hence, it breaks the string by only taking one delimiter from the end. If the string contains more than one delimiter and if 2 is passed as an argument, then the rsplit function will split the string from the second last delimiter as well as the last delimiter.

Removing Whitespace with split()

The following steps help you to remove whitespace using the split method in Python.

Step 1: Split a string and remove whitespace:

This step involves using the str.split() method to split a string into a list. It uses a delimiter to split a string into a list of substrings.

The only argument involved in this method is a separator. It splits the string every time a comma appears. 

Step 2:  Using a list of comprehension to iterate on the strings list.

This step allows the user to define a list of comprehension for which the list of strings must be iterated.

Step 3: Using the str.strip() method:

This step uses the str.strip() method on every iteration to eliminate any leading or following whitespace from the string. The method returns a copy of the string in which the leading and trailing whitespace is removed.

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Handling Empty Strings and Other Edge Cases

When using the.split() method, there may be situations in which the output list incorporates missing values or empty strings. The split() method will show the ValueError if a separator has an empty string.

Let’s understand how the split function handles empty strings with the following example.

data = ",potato,onion,cabbage,,peas,"
vegetables = data.split(',')
print(vegetables)

Output:

['', 'potato', 'onion', ‘cabbage’, '', 'peas', '']

The above output is not ideal due to the empty strings. You can use a list of comprehension to remove those empty strings from the defined list. Here’s how to do it:

vegetables = ['', 'onion', 'radish', 'coriander', '']
vegetables = [vegetable for vegetable in vegetables if vegetable != '']
print(vegetables)

Output:

['onion', 'radish', 'coriander']

Performance Considerations

The split function in Python offers an efficient way to parse strings. The best way to make the most of it is by knowing its performance considerations for accurate implementation. Let’s navigate some of the most prominent ones:

Size of the String: As splitting a large string can be a pretty time-taking process, especially if the string is not cached in memory- a split() function’s performance is significantly affected by an input string’s size.

Delimiter: The split() function uses regular expressions to split strings, which can get slower for complex delimiters. Simple delimiters like space, tab and commas take lesser time to split.

Number of splits: If the number of splits is expansive, it can cause the function to leverage more resources and run slower. To limit the number of splits, you can utilise the optional maxsplit parameter.

Memory usage: The split() function generates a new list object every time it splits a string. Challenges such as memory issues are bound to occur while dealing with larger strings. One way to mitigate this is by using a generator expression, which does not create a new list object but instead generates the split strings on-the-fly.

Conclusion and Further Learning Opportunities.

To sum up, the split() function is a versatile tool that can be used in a wide range of Python programs and applications. It is particularly useful when working with text data or when manipulating strings.

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