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Finding Substrings in Strings: Comprehensive Guide and Practical Examples

Finding Substrings in Strings: Comprehensive Guide and Practical Examples

January 14, 2025 Education

How to Find Substrings in Strings: Comprehensive Guide and Practical Examples

When working with strings in programming, one of the most common tasks is finding substrings within a given string. This guide will explore how to accomplish this in various popular programming languages, including Python, JavaScript, Java, and C. Additionally, we will demonstrate a practical example using the Plain English programming system to search for substrings in a list of strings.

Introduction to Substring Searching

Substrings are portions of a string, and finding them is essential for many applications such as text manipulation, data analysis, and natural language processing. Most programming languages provide built-in functions and methods to facilitate this task. The methods available depend on the specific language and its version, but generally, you can use in-built functions or methods like contains, find, includes, and indexOf.

Examples in Popular Programming Languages

Python

Python offers clean and straightforward methods to find substrings. Here are examples of using the in keyword and the find method:

Using the in keyword:

string  "hello world"substring  "world"if substring in string:    print("Substring found")

Using the find method:

string  "hello world"substring  "world"index  (substring)if index ! -1:    print(f"Substring found at index {index}")

JavaScript

JavaScript provides similar functionality with the includes method and the indexof method:

Using the includes method:

let string  "hello world"let substring  "world"if ((substring)) {    console.log("Substring found")}

Using the indexof method:

let string  "hello world"let substring  "world"let index  (substring)if (index ! -1) {    console.log(`Substring found at index ${index}`)}

Java

In Java, you can use the contains method or the indexof method:

Using the contains method:

String string  "hello world"String substring  "world"if ((substring)) {    }

Using the indexof method:

String string  "hello world"String substring  "world"int index  (substring)if (index ! -1) {    }

C

C also offers similar functionality in terms of string manipulation. While C does not have built-in string manipulation functions like high-level languages, you can create custom functions to achieve the same results:

Using a custom Contains function:

string str  "hello world"string substr  "world"if (Contains(str, substr)) {        printf("Substring found")}

Using a custom IndexOf function:

string str  "hello world"string substr  "world"int index  IndexOf(str, substr)if (index ! -1) {        printf("Substring found at index %d", index)}

The specific methods you use may depend on your requirements, such as case sensitivity, the programming language, and the specific use case. Most languages provide straightforward ways to check for substrings and obtain their indices. If you have a particular language in mind or need further details, feel free to ask!

Practical Example: Plain English Programming System

The Plain English programming system offers a unique approach to string manipulation, especially when working with large text datasets. The system includes simple strings and string things that can be linked into a list of strings. This allows for efficient processing and searching of large bodies of text, such as an entire Bible.

Setting Up and Searching for Substrings

Here is an example of how to search for a substring in a list of strings using the Plain English programming system:

Define and initialize the list of strings and the substring to search for:

The Plain English system also has a library of handy types, variables, and routines, including this type... this global variable... a routine with this header... will populate the Bible variable defined above with the 31000-some verses of the King James version of the Bible when called like this:

Create a subroutine to search for and count verses containing a specific substring:

Subroutine

Create a subroutine to display the first seven verses containing the given substring:

Subroutine

Write a main routine to test the subroutines above:

Main

An example test run of the system can be seen in the following screenshot (click to enlarge):

Conclusion

As you can see, the Plain English programming system provides a powerful and flexible approach to working with large datasets. By utilizing the built-in string manipulation routines and library, you can efficiently search for and process substrings in complex text datasets. Whether you are working with Python, JavaScript, Java, C, or the Plain English programming system, finding substrings in strings is a fundamental skill every programmer should master.

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