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io.IOBase

abstract bases

The abstract base class of all I/O streams (files and StringIO/BytesIO); it defines the shared close/readable/writable/seekable interface.

Syntax

issubclass(cls, io.IOBase)

isinstance(obj, io.IOBase) only confirms that something is a stream, not that it can be read or written: read() and write() are introduced by subclasses, while IOBase itself provides close(), with-statement support and the readable()/writable()/seekable() queries. Touching an already closed stream raises ValueError about an I/O operation on a closed file, not OSError — catch ValueError.

Examples

import io
print(issubclass(io.RawIOBase, io.IOBase))   # → True
print(isinstance(io.StringIO(), io.IOBase))   # → True
print(issubclass(io.TextIOBase, io.IOBase))   # → True
s = io.StringIO('abc')
print(s.readable(), s.writable(), s.seekable())   # → True True True
s.close()
print(s.closed)   # → True
print(s.read())   # → ValueError

See also

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