Parsing a string can mean different things in Python. You can parse a string by splitting or extracting the substrings.

You can also parse a string by converting it to an integer or float variable. Although this should be categorized as a type conversion operation, you'll come across resources that refer to it as string parsing.

In this article, you'll learn how to parse a string using the split() and strip() methods. You'll also learn how to convert a string to an integer using the int() function.

How To Parse a String in Python Using the split() Method

You can use the split() method in Python to "split" substrings of a string into a list.

Here's what the parameter looks like: 

string.split(separator, maxsplit)

The split() method has two optional parameters:

  • separator specifies where to start splitting from (you'll understand this better with the examples in the next section).
  • maxsplit specifies the maximum number of splits.

split() Method Example #1 - How To Use the Separator Parameter

favorite_languages = "JavaScript, Python, and Java"

lang_split = favorite_languages.split(",")

print(lang_split)
# ['JavaScript', ' Python', ' and Java']

In the example above, we created a string called favorite_languages which had three substrings: "JavaScript, Python, and Java".

Using the split() method, we specified that each substring should be split after each comma in the string: favorite_languages.split(",").

The result was a list of each substring: ['JavaScript', ' Python', ' and Java'].

This example shows how to use the first parameter of the split() method. The next example will help you understand the second parameter.

split() Method Example #2 - How To Use the Maxsplit Parameter

favorite_languages = "JavaScript, Python, and Java"

lang_split = favorite_languages.split(",", 1)

print(lang_split)
# ['JavaScript', ' Python, and Java']

In the code above, we made use of the maxsplit parameter which specifies the number of splits to be performed.

So favorite_languages.split(",", 1) means that only one substring should be split, while the rest would remain as they were in the original string.

In the output of the code, only JavaScript was split, while Python and Java retained their initial positions in the string. That is: ['JavaScript', ' Python, and Java'].

How To Parse a String in Python Using the strip() Method

You can use the strip() method to remove white spaces or specified characters in a string.

Here's what the syntax looks like:

string.strip([chars])

The chars parameter specifies the set of characters to be removed. This parameter is optional, so leaving the parenthesis empty will only remove white spaces.

Let's see some examples.

strip() Method Example #1

username = "       Doe      "

user = username.strip()

print(user) 
# Doe

In the example above, we had a string with leading and trailing whitespace characters: "       Doe      ".

Using the strip method without any parameter, we got rid of the whitespaces: username.strip().

In the next example, we'll pass in parameters to the strip() method.

strip() Method Example #2

In this section, we'll use a string that has different characters in it that aren't whitespaces: 

username = "=+---Doe---+="

The goal here is to get rid of the unwanted characters (=+-) found in the username variable.

If you use the strip() method without any parameters, it won't get rid of those characters. Without parameters, the strip() method only removes whitespaces.

To remove the characters in the string, you have to use them as a parameter to tell the strip() method that they should be removed. That is: 

username = "=+---Doe---+="

user = username.strip("=+-")

print(user) 
# Doe

In the code above, we passed in the characters to be removed from the string as a parameter to the strip() method: username.strip("=+-").

Note that you have to nest those characters in quotation marks ("=+-").

How To Convert a String to an Integer Using the int() Function

Data type conversion helps you perform certain operations that involve incompatible data types.

For instance, the example below shows what happens when you try to add an integer and a string: 

age = "300"

print(age + 300) 
# TypeError: can only concatenate str (not "int") to str

In the code above, we created a string value with a value of "300". When we tried adding it to an integer value of 300, we got an error.

The error is thrown because the compiler assumes we're trying to add two strings. String concatenation in Python cannot be performed using a string and an integer.

To solve this problem, you can convert the string to an integer before using it in a mathematical operation.

Here's how you can do that using the int() function:

age = "300"

age_to_int = int(age)

print(age_to_int + 300) 
# 600

In the code above, we used the int() function to convert the age string to an integer: int(age).

Now, you're to use the variable as an integer.

A common use case for converting from a string to an integer is seen when getting input from a user. You can see an example like that in this article.

Summary

In this article, we talked about parsing strings in Python.

We saw examples that showed how to parse a string using the split() and strip() methods.

We also saw how to convert a string to an integer using the int() function.

Happy coding! I also write about Python on my blog.