How to Find String in List in Python

1. Use the for Loop to Find Elements From a List That Contain a Specific Substring in Python
2. Use the filter() Function to Find Elements From a Python List Which Contain a Specific Substring
3. Use the Regular Expressions to Find Elements From a Python List Which Contain a Specific Substring

This tutorial will introduce how to find elements from a Python list that have a specific substring in them.

We will work with the following list and extract strings that have ack in them.

my_list = ["Jack", "Mack", "Jay", "Mark"]

Use the for Loop to Find Elements From a List That Contain a Specific Substring in Python

In this method, we iterate through the list and check whether the substring is present in a particular element or not. If the substring is present in the element, then we store it in the string. The following code shows how:

str_match = [s for s in my_list if "ack" in s]
print(str_match)

Output:

['Jack', 'Mack']

The in keyword checks whether the given string, "ack" in this example, is present in the string or not. It can also be replaced by the __contains__ method, which is a magic method of the string class. For example:

str_match = [s for s in my_list if s.__contains__("ack")]
print(str_match)

Output:

['Jack', 'Mack']

Use the filter() Function to Find Elements From a Python List Which Contain a Specific Substring

The filter() function retrieves a subset of the data from a given object with the help of a function. This method will use the lambda keyword to define the condition for filtering data. The lambda keyword creates a one-line lambda function in Python. See the following code snippet.

str_match = list(filter(lambda x: "ack" in x, my_list))
print(str_match)

Output:

['Jack', 'Mack']

Use the Regular Expressions to Find Elements From a Python List Which Contain a Specific Substring

A regular expression is a sequence of characters that can act as a matching pattern to search for elements. To use regular expressions, we have to import the re module. In this method, we will use the for loop and the re.search() method, which is used to return an element that matches a specific pattern. The following code will explain how:

import re

pattern = re.compile(r"ack")
str_match = [x for x in my_list if re.search("ack", x)]
print(str_match)

Output:

['Jack', 'Mack']