How to Filter Strings Containing a Specific Substring in Python?

Filtering Strings Containing Specific Content

Filtering a list of strings based on content is a common task in programming. In this case, we want to extract all strings from a list that contain the substring "ab". This can be achieved in various ways in Python.

List Comprehensions

The most efficient approach is to use list comprehensions, which combine list iteration and conditional filtering in one expression. Here's how you can do it:

<code class="python">lst = ['a', 'ab', 'abc', 'bac']
ab_strings = [k for k in lst if 'ab' in k]
print(ab_strings)</code>

Output:

['ab', 'abc']

Filter Function

Another option is to use the filter function, which iterates through a list and applies a filtering criterion specified by a lambda function. In Python 2, you can use it as follows:

<code class="python">ab_strings = filter(lambda k: 'ab' in k, lst)</code>

In Python 3, filter returns an iterator instead of a list, so you can either iterate over it directly or cast it to a list:

<code class="python"># Option A: Iterate over the iterable
for k in ab_strings:
    print(k)

# Option B: Cast to a list
ab_strings = list(ab_strings)
print(ab_strings)</code>

Conclusion

Both list comprehensions and the filter function provide effective ways to filter a list of strings based on specific content. However, list comprehensions are generally preferred for their concise and readable syntax.

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