all Python 3Byte sequencesfunction

bytes.islower

bytes — is* checks

Check that all cased bytes are lower-case.

Syntax

b.islower(...)

A common trap: islower() is not the negation of isupper(). When there are no cased bytes at all (b'123', b'!!!', b''), both return False, so "not lower-case therefore upper-case" is a wrong inference. Only ASCII letters count as cased here: a byte like b'\xe9' (é in latin-1) is not a letter for this check, so decode to str first when the data is not ASCII.

Examples

print(b'abc'.islower())   # → True
print(b'abc1!'.islower())   # → True
print(b'Hello'.lower().islower())   # → True
print(b'Abc'.islower())   # → False
print(b'123'.islower())   # → False
print(b''.islower())   # → False

See also

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