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Use Python’s built-in str.startswith() method. It returns True when a string begins with the given prefix and False otherwise.
Check for one prefix
Call startswith() on the string and pass the prefix you want to test:
text = "Python programming"
prefix = "Python"
if text.startswith(prefix):
print("The string starts with the prefix")The method’s form is str.startswith(prefix[, start[, end]]). The comparison uses the text as provided, so it is case-sensitive: "Python" matches the beginning of "Python programming", but not "python programming". Python’s built-in types documentation describes the method and its return value.
Check for one of several prefixes
Pass a tuple when any one of several complete prefixes should count as a match:
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url = "https://example.com"
if url.startswith(("http://", "https://")):
print("The URL uses a supported scheme")Each tuple member is checked as a candidate prefix. A tuple is not a set of individual characters; for example, ("http://", "https://") tests those two full beginnings.
Check a prefix at a particular position
Use the optional start and end arguments to limit the comparison to a region of the string. For example, this checks whether "programming" begins at position 7:
text = "Python programming"
text.startswith("programming", 7) # TrueThe range arguments let you make the check without first creating a sliced string. The documentation establishes the range behavior; it does not establish a performance advantage.
Perform a caseless Unicode prefix check
startswith() does not ignore case automatically. For caseless Unicode matching, casefold both the string and the prefix before checking:
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text = "Straße"
prefix = "STRASSE"
text.casefold().startswith(prefix.casefold()) # TruePython documents casefolded strings as useful for caseless matching. Casefolding is more aggressive than lowercasing; for example, "straße".lower() remains "straße", while "straße".casefold() becomes "strasse". See the Python documentation for str.casefold().
Remove a matching prefix instead of checking it
If you need the resulting string with a matching prefix removed, use removeprefix():
text = "TestHook"
text.removeprefix("Test") # "Hook"If the prefix does not match, removeprefix() returns the original string. It was added in Python 3.9. Use startswith() when you only need a yes-or-no check. Python documents removeprefix() and its version history.
Check a prefix in binary data
bytes and bytearray also provide startswith(). Pass a bytes-like prefix, or use a tuple of prefixes and the optional range positions:
data = b"Python data"
data.startswith(b"Python") # TrueFor these binary types, use a bytes-like prefix such as b"Python", rather than a text string. The Python documentation covers bytes and bytearray prefix checks.
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