Python string startswith() and endswith() methods

Python string startswith() and endswith() methods

The startswith() and endswith() methods are built-in Python string methods used to check whether a string starts or ends with the specified substring or sequence of substrings. Both methods return a boolean value: True if the string starts or ends with the specified substring(s) and False otherwise.

Here is a step-by-step tutorial on how to use the startswith() and endswith() methods in Python:

  1. Syntax:

    The startswith() and endswith() methods have the following syntax:

    string.startswith(prefix, start, end) string.endswith(suffix, start, end)
    • prefix / suffix: The substring or a tuple of substrings to check if the string starts/ends with.
    • start: (Optional) The starting index of the search. Defaults to 0.
    • end: (Optional) The ending index of the search. Defaults to the length of the string.

  2. Basic usage:

    To check if a string starts or ends with a specific substring, call the startswith() or endswith() method with the desired substring as an argument:

    text = "Hello, how are you?" starts_with_hello = text.startswith("Hello") ends_with_question = text.endswith("?") print(starts_with_hello) # Output: True print(ends_with_question) # Output: True

  3. Using start and end parameters:

    You can limit the search by specifying the start and end parameters:

    text = "Hello, how are you?" starts_with_how = text.startswith("how", 7, 10) ends_with_are = text.endswith("are", 0, 14) print(starts_with_how) # Output: True print(ends_with_are) # Output: True

  4. Checking multiple substrings:

    You can use a tuple of substrings to check if a string starts or ends with any of the specified substrings:

    text = "example.txt" starts_with = text.startswith(("example", "sample")) ends_with = text.endswith((".txt", ".md")) print(starts_with) # Output: True print(ends_with) # Output: True

In summary, the startswith() and endswith() methods are useful for checking whether a string starts or ends with a specific substring or sequence of substrings. They are commonly used in tasks like string validation, filtering, and pattern matching.

Examples

  1. How to Use startswith() in Python for String Matching:

    • Use startswith() to check if a string starts with a specified prefix.
    # Example text = "Python is powerful" starts_with_python = text.startswith("Python")

  2. Checking String Endings with endswith() in Python:

    • Use endswith() to check if a string ends with a specified suffix.
    # Example file_name = "document.txt" is_text_file = file_name.endswith(".txt")

  3. Conditional Statements Using startswith() in Python:

    • Employ startswith() in conditional statements for prefix-based checks.
    # Example text = "Hello, World!" if text.startswith("Hello"): print("Greeting detected.")

  4. String Prefix Matching with startswith() in Python:

    • Perform string prefix matching using startswith().
    # Example sentence = "Python programming is fun" starts_with_python = sentence.startswith("Python")

  5. Python endswith() for Checking Suffixes:

    • Utilize endswith() to check if a string has a specified suffix.
    # Example file_name = "image.jpg" is_image_file = file_name.endswith((".jpg", ".png"))

  6. Matching Multiple Prefixes with startswith() in Python:

    • Check if a string starts with any of the specified prefixes using startswith().
    # Example text = "Python is versatile" starts_with_languages = text.startswith(("Python", "Java", "C++"))

  7. Case-Insensitive Matching with startswith() and endswith() in Python:

    • Perform case-insensitive matching using lower() or casefold().
    # Example text = "Python is case-insensitive" starts_with_python = text.lower().startswith("python")

  8. Handling Unicode Characters with startswith() and endswith() in Python:

    • Use startswith() and endswith() with Unicode characters.
    # Example unicode_text = "𝒫ython 𝒾s ℂool" starts_with_unicode = unicode_text.startswith("𝒫")

  9. Efficient Ways to Use startswith() and endswith() in Python:

    • Optimize performance by using startswith() and endswith() judiciously.
    # Example text = "Efficient programming" is_efficient = text.startswith("Eff") and text.endswith("ing")

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