How to Filter a List of Strings by Keyword in Python

def filter_strings(items, keyword, case_sensitive=False):
    """
    Filter a list of strings by a keyword.
    
    Args:
        items: list of strings to filter
        keyword: substring to search for
        case_sensitive: if True, match case exactly
    
    Returns:
        list of strings containing the keyword
    """
    if case_sensitive:
        return [item for item in items if keyword in item]
    else:
        keyword_lower = keyword.lower()
        return [item for item in items if keyword_lower in item.lower()]


if __name__ == "__main__":
    sample_data = [
        "Python programming",
        "Data Science basics",
        "python for beginners",
        "Web Development",
        "Machine Learning with Python"
    ]
    
    print("Filter 'python' (case-insensitive):")
    print(filter_strings(sample_data, "python"))
    
    print("\nFilter 'python' (case-sensitive):")
    print(filter_strings(sample_data, "python", case_sensitive=True))
    
    print("\nFilter 'data':")
    print(filter_strings(sample_data, "data"))