How to Filter Strings Based on Specific Substring Content in Python?

Filtering Strings with Specific Content

In this programming question, we seek a solution to filter a list of strings based on their contents. Given a list such as ['a', 'ab', 'abc', 'bac'], our goal is to extract a list that contains only strings with a specific substring, such as 'ab'.

Python Implementation

To achieve this filtering in Python, we can employ various methods. One efficient approach involves the use of list comprehensions:

<code class="python">lst = ['a', 'ab', 'abc', 'bac']
result = [k for k in lst if 'ab' in k]

# Result: ['ab', 'abc']</code>

In this code, we iterate through the original list using a comprehension and check if each string contains the substring 'ab' using the 'in' operator. Only strings that satisfy this condition are included in the result list.

Another option is to leverage the filter function:

Python 2:

<code class="python">from itertools import ifilter
lst = ['a', 'ab', 'abc', 'bac']
result = ifilter(lambda k: 'ab' in k, lst)

# Result: ['ab', 'abc']</code>

Python 3:

<code class="python">lst = ['a', 'ab', 'abc', 'bac']
result = list(filter(lambda k: 'ab' in k, lst))

# Result: ['ab', 'abc']</code>

In Python 3, filter returns an iterator. To obtain a list, we explicitly cast it using the list() function. While the filter function provides another way to perform the filtering, list comprehensions are generally considered more concise and efficient for this type of operation.

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