strstartswith

Strstartswith is a method of Python's built-in string type used to determine whether a string begins with a specified prefix. It is called on a string object as s.startswith(prefix, start, end) and returns a boolean value. The method accepts a single string prefix or a tuple of strings as the prefix argument. If a tuple is provided, the method returns True if the string starts with any of the elements in the tuple.

Parameters and behavior: prefix is required and can be a string or a tuple of strings. Start and end are optional integer indices that limit the portion of the string examined; if omitted, start defaults to 0 and end defaults to the string's length. The comparison is case-sensitive and locale-insensitive. Negative indices are allowed and count from the end of the string.

Tuple handling: When a tuple of prefixes is given, every element must be a string. The method will return True if the substring defined by the optional start and end range starts with any of the prefixes in the tuple.

Performance and usage: str.startswith is implemented in C and is generally efficient for simple prefix checks. It is commonly used in input validation, URL parsing, and file type detection. It is complementary to endswith, which checks for suffixes rather than prefixes.

Examples:

- "hello world".startswith("hello") -> True

- "https://example.com".startswith("http://", "https://") -> True

- "http://example.com".startswith("https://", 0, 5) -> False

See also: endswith for suffix checks, and the broader family of string matching methods in Python.